Eslint Release Notes

Highlights

This release updates the minimatch dependency to v10.2.1 which includes the fix for a recently published security issue.

Bug Fixes

• c87d5bd fix: update eslint (#20531) (renovate[bot])
• d841001 fix: update minimatch to 10.2.1 to address security vulnerabilities (#20519) (루밀LuMir)
• 04c2147 fix: update error message for unused suppressions (#20496) (fnx)
• 38b089c fix: update dependency @eslint/config-array to ^0.23.1 (#20484) (renovate[bot])

Documentation

• 5b3dbce docs: add AI acknowledgement section to templates (#20431) (루밀LuMir)
• 6f23076 docs: toggle nav in no-JS mode (#20476) (Tanuj Kanti)
• b69cfb3 docs: Update README (GitHub Actions Bot)

Chores

• e5c281f chore: updates for v9.39.3 release (Jenkins)
• 8c3832a chore: update @typescript-eslint/parser to ^8.56.0 (#20514) (Milos Djermanovic)
• 8330d23 test: add tests for config-api (#20493) (Milos Djermanovic)
• 37d6e91 chore: remove eslint v10 prereleases from eslint-config-eslint deps (#20494) (Milos Djermanovic)
• da7cd0e refactor: cleanup error message templates (#20479) (Francesco Trotta)
• 84fb885 chore: package.json update for @eslint/js release (Jenkins)
• 1f66734 chore: add eslint to peerDependencies of @eslint/js (#20467) (Milos Djermanovic)

Original source Report a problem

We just pushed ESLint v9.39.3, which is a patch release upgrade of ESLint. This release fixes several bugs found in the previous release.

Highlights

This version restores TypeScript 4.0 compatibility in types.

Bug Fixes

• 791bf8d fix: restore TypeScript 4.0 compatibility in types (#20504) (sethamus)

Chores

• 8594a43 chore: upgrade @eslint/[email protected] (#20529) (Milos Djermanovic)
• 9ceef92 chore: package.json update for @eslint/js release (Jenkins)
• af498c6 chore: ignore /docs/v9.x in link checker (#20453) (Milos Djermanovic)

Original source Report a problem

We just pushed ESLint v10.0.0, which is a major release upgrade of ESLint. This release adds some new features and fixes several bugs found in the previous release. This release also has some breaking changes, so please read the following closely.

ESLint v10.0.0 is a major release that includes several new features and breaking changes. Here are some of the most notable updates.

Installing
Because this is a major release, you may not automatically be upgraded by npm. To ensure you are using this version, run:
npm i [email protected] --save-dev

Node.js < v20.19.0, v21.x, v23.x no longer supported
As of this post, Node.js v24.x is the LTS release, and as such we are dropping support for all versions of Node.js prior to v20.19.0 as well as v21.x and v23.x.

Migration Guide
As there are a lot of changes, we’ve created a migration guide describing the breaking changes in great detail along with the steps you should take to address them. We expect that most users should be able to upgrade without any build changes, but the migration guide should be a useful resource if you encounter problems.

New configuration file lookup algorithm
ESLint v10.0.0 locates eslint.config.* by starting from the directory of each linted file rather than the current working directory as was the case with ESLint v9.x. The new behavior allows for using multiple configuration files in the same run and can be particularly useful in monorepo setups.

In ESLint v9.x, this config lookup behavior could be enabled with the v10_config_lookup_from_file feature flag. In ESLint v10.0.0, this behavior is now the default and the v10_config_lookup_from_file flag has been removed.

Removed eslintrc functionality
As announced in Flat config rollout plans, the eslintrc config system has been completely removed in ESLint v10.0.0. Specifically, this means:

1. The ESLINT_USE_FLAT_CONFIG environment variable is no longer honored.
2. The CLI no longer supports eslintrc-specific arguments (--no-eslintrc, --env, --resolve-plugins-relative-to, --rulesdir, --ignore-path).
3. .eslintrc.* and .eslintignore files will no longer be honored.
4. /* eslint-env */ comments are reported as errors.
5. The loadESLint() function now always returns the ESLint class.
6. The Linter constructor configType argument can only be "flat" and will throw an error if "eslintrc" is passed.
7. The following Linter eslintrc-specific methods are removed: defineParser(), defineRule(), defineRules(), getRules().
8. The following changes to the /use-at-your-own-risk entrypoint: LegacyESLint is removed, FileEnumerator is removed, shouldUseFlatConfig() function will always return true.

JSX references are now tracked
ESLint v10.0.0 now tracks JSX references, enabling correct scope analysis of JSX elements.
Previously, JSX identifiers weren’t tracked as references, which could lead to incorrect results in rules relying on scope information. For example:
import { Card } from "./card.jsx";
export function createCard(name) {
return ;
}
Prior to v10.0.0:
• False positives: could be reported as “defined but never used” (no-unused-vars).
• False negatives: Removing the import might not trigger an “undefined variable” error (no-undef).
Starting with v10.0.0, is treated as a normal reference to the variable in scope. This eliminates confusing false positives/negatives, aligns JSX handling with developer expectations, and improves the linting experience in projects using JSX.

Espree and ESLint Scope now include types
Beginning with Espree v11.1.0 and ESLint Scope v9.1.0, these packages now contain built-in type definitions.
Previously, type definitions were provided by Definitely Typed packages @types/espree and @types/eslint-scope. There are several differences between the old and new type definitions, mostly bug fixes. If your code relies on types for the Espree and ESLint Scope packages, check if there are any updates needed.

Enhancements to RuleTester
Since its earliest days, ESLint has provided the RuleTester API to help plugin authors test their rules against custom test cases and configurations. This release introduces several enhancements to RuleTester to enforce more robust test definitions and improve debugging.

Assertion options
The RuleTester#run() method now supports assertion options, specifically requireMessage, requireLocation, and requireData, to let developers enforce stricter requirements in rule tests. These options enforce that every invalid test case explicitly checks violation messages, locations, and data, ensuring that a test fails if it doesn’t meet the requirements.
• requireMessage
◦ Ensures every test case includes a message check.
◦ Accepts:
■ true: Must use an array of objects for errors, rather than a numeric count shorthand, to check the problems reported by a rule. Each object must include a message or messageId property as usual to check the message of a reported problem.
■ "message": Must check using message only.
■ "messageId": Must check using messageId only.
◦ Purpose: Prevents tests from passing without verifying the actual message.
• requireLocation
◦ Ensures every test case includes a location check.
◦ Accepts:
■ true
◦ Requires line and column in each object of the errors array.
◦ endLine and endColumn are optional if the actual report doesn’t include them.
◦ Purpose: Guarantees that tests validate the location of an error.
• requireData
◦ Ensures every test case includes a data check.
◦ Accepts:
■ true
◦ When set to true, RuleTester will require invalid test cases to include a data object whenever a messageId references a message with placeholders. This helps ensure that tests remain consistent with rule messages that rely on placeholder substitution.

Example Usage:
ruleTester.run("my-rule", rule, {
valid: [
{ code: "var foo = true;" }
],
invalid: [
{
code: "var invalidVariable = true;",
errors: [
{
message: "Unexpected invalid variable.",
line: 1,
column: 5
}
]
}
],
assertionOptions: {
requireMessage: true,
requireLocation: true
}
});

Improved location reporting for failing tests
RuleTester now decorates stack traces with information that makes it easier to locate failing test cases in your source code. For example, the test output will now include stack trace lines indicating the index of the failing test case in the invalid array and the file and line number where that test case is defined.
Note that these line numbers may not always be included, depending on how your tests are structured. When the lines cannot be determined precisely, the failing test index and the printed code snippet are still available to locate the test case.

countThis option in max-params rule
The max-params rule now supports the new countThis option, which supersedes the deprecated countVoidThis. With the setting countThis: "never", the rule will now ignore any this annotation in a function’s argument list when counting the number of parameters in a TypeScript function. For example:
function doSomething(this: SomeType, first: string, second: number) {
// ...
}
will be considered a function taking only 2 parameters.

color property in formatter context
When the --color or --no-color option is specified on the command line, ESLint sets an additional color property on the context object passed to a formatter (the second argument of the format() method). This property is true for --color and false for --no-color.
Custom formatters can use this value to determine whether to apply color styling, based on the assumption that the terminal supports or does not support colors as indicated by the option.

Updated eslint:recommended
The eslint:recommended configuration is updated to include new rules that we feel are important.

Removed deprecated rule context members
The following rule context members are no longer available:
• context.getCwd() - Use context.cwd instead
• context.getFilename() - Use context.filename instead
• context.getPhysicalFilename() - Use context.physicalFilename instead
• context.getSourceCode() - Use context.sourceCode instead
• context.parserOptions - Use context.languageOptions or context.languageOptions.parserOptions instead
• context.parserPath - No replacement

Removed deprecated SourceCode methods
The following SourceCode methods are no longer available:
• getTokenOrCommentBefore() - Use getTokenBefore() with the { includeComments: true } option instead
• getTokenOrCommentAfter() - Use getTokenAfter() with the { includeComments: true } option instead
• isSpaceBetweenTokens() - Use isSpaceBetween() instead
• getJSDocComment() - No replacement

Program AST node range spans entire source text
Starting with ESLint v10.0.0, Program AST node’s range spans the entire source text. Previously, leading and trailing comments/whitespace were not included in the range.

Jiti < v2.2.0 no longer supported
ESLint v10.0.0 drops support for jiti versions prior to 2.2.0 when loading TypeScript configuration files due to known issues that can cause compatibility problems when configurations load certain plugins.

Breaking Changes
• f9e54f4 feat!: estimate rule-tester failure location (#20420) (ST-DDT)
• a176319 feat!: replace chalk with styleText and add color to ResultsMeta (#20227) (루밀LuMir)
• c7046e6 feat!: enable JSX reference tracking (#20152) (Pixel998)
• fa31a60 feat!: add name to configs (#20015) (Kirk Waiblinger)
• 3383e7e fix!: remove deprecated SourceCode methods (#20137) (Pixel998)
• 501abd0 feat!: update dependency minimatch to v10 (#20246) (renovate[bot])
• ca4d3b4 fix!: stricter rule tester assertions for valid test cases (#20125) (唯然)
• 96512a6 fix!: Remove deprecated rule context methods (#20086) (Nicholas C. Zakas)
• c69fdac feat!: remove eslintrc support (#20037) (Francesco Trotta)
• 208b5cc feat!: Use ScopeManager#addGlobals() (#20132) (Milos Djermanovic)
• a2ee188 fix!: add uniqueItems: true in no-invalid-regexp option (#20155) (Tanuj Kanti)
• a89059d feat!: Program range span entire source text (#20133) (Pixel998)
• 39a6424 fix!: assert ‘text’ is a string across all RuleFixer methods (#20082) (Pixel998)
• f28fbf8 fix!: Deprecate "always" and "as-needed" options of the radix rule (#20223) (Milos Djermanovic)
• aa3fb2b fix!: tighten func-names schema (#20119) (Pixel998)
• f6c0ed0 feat!: report eslint-env comments as errors (#20128) (Francesco Trotta)
• 4bf739f fix!: remove deprecated LintMessage#nodeType and TestCaseError#type (#20096) (Pixel998)
• 523c076 feat!: drop support for jiti < 2.2.0 (#20016) (michael faith)
• 454a292 feat!: update eslint:recommended configuration (#20210) (Pixel998)
• 4f880ee feat!: remove v10_* and inactive unstable_* flags (#20225) (sethamus)
• f18115c feat!: no-shadow-restricted-names report globalThis by default (#20027) (sethamus)
• c6358c3 feat!: Require Node.js ^20.19.0 || ^22.13.0 || >=24 (#20160) (Milos Djermanovic)

Features
• bff9091 feat: handle Array.fromAsync in array-callback-return (#20457) (Francesco Trotta)
• 290c594 feat: add self to no-implied-eval rule (#20468) (sethamus)
• 43677de feat: fix handling of function and class expression names in no-shadow (#20432) (Milos Djermanovic)
• f0cafe5 feat: rule tester add assertion option requireData (#20409) (fnx)
• f7ab693 feat: output RuleTester test case failure index (#19976) (ST-DDT)
• 7cbcbf9 feat: add countThis option to max-params (#20236) (Gerkin)
• f148a5e feat: add error assertion options (#20247) (ST-DDT)
• 09e6654 feat: update error loc of require-yield and no-useless-constructor (#20267) (Tanuj Kanti)

Bug Fixes
• 436b82f fix: update eslint (#20473) (renovate[bot])
• 1d29d22 fix: detect default this binding in Array.fromAsync callbacks (#20456) (Francesco Trotta)
• 727451e fix: fix regression of global mode report range in strict rule (#20462) (ntnyq)
• e80485f fix: remove fake FlatESLint and LegacyESLint exports (#20460) (Francesco Trotta)
• 9eeff3b fix: update esquery (#20423) (cryptnix)
• b34b938 fix: use Error.prepareStackTrace to estimate failing test location (#20436) (Francesco Trotta)
• 51aab53 fix: update eslint (#20443) (renovate[bot])
• 23490b2 fix: handle space before colon in RuleTester location estimation (#20433) (Francesco Trotta)
• f244dbf fix: use MessagePlaceholderData type from @eslint/core (#20348) (루밀LuMir)
• d186f8c fix: update eslint (#20427) (renovate[bot])
• 2332262 fix: error location should not modify error message in RuleTester (#20421) (Milos Djermanovic)
• ab99b21 fix: ensure filename is passed as third argument to verifyAndFix() (#20405) (루밀LuMir)
• 8a60f3b fix: remove ecmaVersion and sourceType from ParserOptions type (#20415) (Pixel998)
• eafd727 fix: remove TDZ scope type (#20231) (jaymarvelz)
• 39d1f51 fix: correct Scope typings (#20404) (sethamus)
• 2bd0f13 fix: update verify and verifyAndFix types (#20384) (Francesco Trotta)
• ba6ebfa fix: correct typings for loadESLint() and shouldUseFlatConfig() (#20393) (루밀LuMir)
• e7673ae fix: correct RuleTester typings (#20105) (Pixel998)
• 53e9522 fix: strict removed formatters check (#20241) (ntnyq)
• b017f09 fix: correct no-restricted-import messages (#20374) (Francesco Trotta)

Documentation
• e978dda docs: Update README (GitHub Actions Bot)
• 4cecf83 docs: Update README (GitHub Actions Bot)
• c79f0ab docs: Update README (GitHub Actions Bot)
• 773c052 docs: Update README (GitHub Actions Bot)
• f2962e4 docs: document meta.docs.frozen property (#20475) (Pixel998)
• 8e94f58 docs: fix broken anchor links from gerund heading updates (#20449) (Copilot)
• 1495654 docs: Update README (GitHub Actions Bot)
• 0b8ed5c docs: document support for :is selector alias (#20454) (sethamus)
• 1c4b33f docs: Document policies about ESM-only dependencies (#20448) (Milos Djermanovic)
• 3e5d38c docs: add missing indentation space in rule example (#20446) (fnx)
• 63a0c7c docs: Update README (GitHub Actions Bot)
• 65ed0c9 docs: Update README (GitHub Actions Bot)
• b0e4717 docs: [no-await-in-loop] Expand inapplicability (#20363) (Niklas Hambüchen)
• fca421f docs: Update README (GitHub Actions Bot)
• d925c54 docs: update config syntax in no-lone-blocks (#20413) (Pixel998)
• 7d5c95f docs: remove redundant sourceType: "module" from rule examples (#20412) (Pixel998)
• 02e7e71 docs: correct .mts glob pattern in files with extensions example (#20403) (Ali Essalihi)
• 264b981 docs: Update README (GitHub Actions Bot)
• 5a4324f docs: clarify "local" option of no-unused-vars (#20385) (Milos Djermanovic)
• e593aa0 docs: improve clarity, grammar, and wording in documentation site README (#20370) (Aditya)
• 3f5062e docs: Add messages property to rule meta documentation (#20361) (Sabya Sachi)
• 9e5a5c2 docs: remove Examples headings from rule docs (#20364) (Milos Djermanovic)
• 194f488 docs: Update README (GitHub Actions Bot)
• 0f5a94a docs: [class-methods-use-this] explain purpose of rule (#20008) (Kirk Waiblinger)
• df5566f docs: add Options section to all rule docs (#20296) (sethamus)
• adf7a2b docs: note for generator functions (#20330) (Tom Pereira)
• ef7028c docs: Update README (GitHub Actions Bot)
• fbae5d1 docs: consistently use “v10.0.0” in migration guide (#20328) (Pixel998)
• 778aa2d docs: ignoring default file patterns (#20312) (Tanuj Kanti)
• 4b5dbcd docs: reorder v10 migration guide (#20315) (Milos Djermanovic)
• 5d84a73 docs: Update README (GitHub Actions Bot)
• 37c8863 docs: fix incorrect anchor link in v10 migration guide (#20299) (Pixel998)
• 077ff02 docs: add migrate-to-10.0.0 doc (#20143) (唯然)
• 3822e1b docs: Update README (GitHub Actions Bot)

Build Related
• 9f08712 Build: changelog update for 10.0.0-rc.2 (Jenkins)
• 1e2c449 Build: changelog update for 10.0.0-rc.1 (Jenkins)
• c4c72a8 Build: changelog update for 10.0.0-rc.0 (Jenkins)
• 7e4daf9 Build: changelog update for 10.0.0-beta.0 (Jenkins)
• a126a2a build: add .scss files entry to knip (#20389) (Francesco Trotta)
• f5c0193 Build: changelog update for 10.0.0-alpha.1 (Jenkins)
• 165326f Build: changelog update for 10.0.0-alpha.0 (Jenkins)

Chores
• 1ece282 chore: ignore /docs/v9.x in link checker (#20452) (Milos Djermanovic)
• 034e139 ci: add type integration test for @html-eslint/eslint-plugin (#20345) (sethamus)
• f3fbc2f chore: set @eslint/js version to 10.0.0 to skip releasing it (#20466) (Milos Djermanovic)
• afc0681 chore: remove scopeManager.addGlobals patch for typescript-eslint parser (#20461) (fnx)
• 3e5a173 refactor: use types from @eslint/plugin-kit (#20435) (Pixel998)
• 11644b1 ci: rename workflows (#20463) (Milos Djermanovic)
• 2d14173 chore: fix typos in docs and comments (#20458) (o-m12a)
• 6742f92 test: add endLine/endColumn to invalid test case in no-alert (#20441) (경하)
• 3e22c82 test: add missing location data to no-template-curly-in-string tests (#20440) (Haeun Kim)
• b4b3127 chore: package.json update for @eslint/js release (Jenkins)
• f658419 refactor: remove raw parser option from JS language (#20416) (Pixel998)
• 2c3efb7 chore: remove category from type test fixtures (#20417) (Pixel998)
• 36193fd chore: remove category from formatter test fixtures (#20418) (Pixel998)
• e8d203b chore: add JSX language tag validation to check-rule-examples (#20414) (Pixel998)
• bc465a1 chore: pin dependencies (#20397) (renovate[bot])
• 703f0f5 test: replace deprecated rules in linter tests (#20406) (루밀LuMir)
• ba71baa test: enable strict mode in type tests (#20398) (루밀LuMir)
• f9c4968 refactor: remove lib/linter/rules.js (#20399) (Francesco Trotta)
• 6f1c48e chore: updates for v9.39.2 release (Jenkins)
• 54bf0a3 ci: create package manager test (#20392) (루밀LuMir)
• 3115021 refactor: simplify JSDoc comment detection logic (#20360) (Pixel998)
• 4345b17 chore: update @eslint-community/regexpp to 4.12.2 (#20366) (루밀LuMir)
• 772c9ee chore: update dependency @eslint/eslintrc to ^3.3.3 (#20359) (renovate[bot])
• 0b14059 chore: package.json update for @eslint/js release (Jenkins)
• d6e7bf3 ci: bump actions/checkout from 5 to 6 (#20350) (dependabot[bot])
• 139d456 chore: require mandatory headers in rule docs (#20347) (Milos Djermanovic)
• 3b0289c chore: remove unused .eslintignore and test fixtures (#20316) (Pixel998)
• a463e7b chore: update dependency js-yaml to v4 [security] (#20319) (renovate[bot])
• ebfe905 chore: remove redundant rules from eslint-config-eslint (#20327) (Milos Djermanovic)
• 88dfdb2 test: add regression tests for message placeholder interpolation (#20318) (fnx)
• 6ed0f75 chore: skip type checking in eslint-config-eslint (#20323) (Francesco Trotta)
• 1e2cad5 chore: package.json update for @eslint/js release (Jenkins)
• 9da2679 chore: update @eslint/* dependencies (#20321) (Milos Djermanovic)
• 0439794 refactor: use types from @eslint/core (#20235) (jaymarvelz)
• cb51ec2 test: cleanup SourceCode#traverse tests (#20289) (Milos Djermanovic)
• 897a347 chore: remove restriction for type in rule tests (#20305) (Pixel998)
• d972098 chore: ignore prettier updates in renovate to keep in sync with trunk (#20304) (Pixel998)
• a086359 chore: remove redundant fast-glob dev-dependency (#20301) (루밀LuMir)
• 564b302 chore: install prettier as a dev dependency (#20302) (michael faith)
• 8257b57 refactor: correct regex for eslint-plugin/report-message-format (#20300) (루밀LuMir)
• e251671 refactor: extract assertions in RuleTester (#20135) (唯然)
• 2e7f25e chore: add legacy-peer-deps to .npmrc (#20281) (Milos Djermanovic)

Original source Report a problem

We just pushed ESLint v10.0.0-rc.2, which is a patch release upgrade of ESLint. This release fixes several bugs found in the previous release.

Highlights

This version of ESLint is not ready for production use and is provided to gather feedback from the community before releasing the final version. Please let us know if you have any problems or feedback by creating issues on our GitHub repo.

Note that this prerelease version of ESLint has a separate documentation section.

Notable bug fixes

• A regression in the core strict rule has been fixed.
• LegacyESLint and FlatESLint exports are now completely removed from the /use-at-your-own-risk entrypoint. In previous prerelease versions of ESLint v10, they were exported as null.

Installing

Since this is a pre-release version, you will not automatically be upgraded by npm. You must specify the next tag when installing:

npm i eslint@next --save-dev

You can also specify the version directly:

npm i [email protected] --save-dev

Migration Guide

As there are a lot of changes, we’ve created a migration guide describing the breaking changes in great detail along with the steps you should take to address them. We expect that most users should be able to upgrade without any build changes, but the migration guide should be a useful resource if you encounter problems.

Bug Fixes

• 727451e fix: fix regression of global mode report range in strict rule (#20462) (ntnyq)
• e80485f fix: remove fake FlatESLint and LegacyESLint exports (#20460) (Francesco Trotta)
• 9eeff3b fix: update esquery (#20423) (cryptnix)

Documentation

• 1495654 docs: Update README (GitHub Actions Bot)
• 0b8ed5c docs: document support for :is selector alias (#20454) (sethamus)
• 1c4b33f docs: Document policies about ESM-only dependencies (#20448) (Milos Djermanovic)

Chores

• 2d14173 chore: fix typos in docs and comments (#20458) (o-m12a)

Original source Report a problem

Highlights

This version of ESLint is not ready for production use and is provided to gather feedback from the community before releasing the final version. Please let us know if you have any problems or feedback by creating issues on our GitHub repo.

Note that this prerelease version of ESLint has a separate documentation section.

Espree and ESLint Scope now include types

Beginning with Espree v11.1.0 and ESLint Scope v9.1.0, these packages now contain built-in type definitions.

Previously, type definitions were provided by Definitely Typed packages @types/espree and @types/eslint-scope. There are several differences between the old and new type definitions, mostly bug fixes. If your code relies on types for the Espree and ESLint Scope packages, check if there are any updates needed.

Installing

Since this is a pre-release version, you will not automatically be upgraded by npm. You must specify the next tag when installing:

npm i eslint@next --save-dev

You can also specify the version directly:

npm i [email protected] --save-dev

Migration Guide

As there are a lot of changes, we’ve created a migration guide describing the breaking changes in great detail along with the steps you should take to address them. We expect that most users should be able to upgrade without any build changes, but the migration guide should be a useful resource if you encounter problems.

Features

• feat: fix handling of function and class expression names in no-shadow (#20432) (Milos Djermanovic)

Bug Fixes

• fix: use Error.prepareStackTrace to estimate failing test location (#20436) (Francesco Trotta)
• fix: update eslint (#20443) (renovate[bot])
• fix: handle space before colon in RuleTester location estimation (#20433) (Francesco Trotta)
• fix: use MessagePlaceholderData type from @eslint/core (#20348) (루밀LuMir)

Documentation

• docs: add missing indentation space in rule example (#20446) (fnx)
• docs: Update README (GitHub Actions Bot)

Chores

• test: add endLine/endColumn to invalid test case in no-alert (#20441) (경하)
• test: add missing location data to no-template-curly-in-string tests (#20440) (Haeun Kim)

Original source Report a problem

Expanding language support: CSS and HTML

Following the release of JSON and Markdown support in 2024, we continued our mission to make ESLint a truly language-agnostic linter. In February, we released official CSS support via the @eslint/css plugin, allowing users to lint their stylesheets with the same familiar configuration system.

In May, we were excited to announce that html-eslint had joined the ESLint ecosystem as a language plugin, bringing robust HTML linting to the project. These additions mean that ESLint can now officially be used to lint the “big three” of the web: JavaScript, CSS, and HTML.

ESLint’s new CSS and HTML support were highlighted in three different talks at Google I/O as well as on the Chrome blog.

ESLint continues to grow

ESLint’s usage continued its relentless climb in 2025. We started the year with 42,717,190 weekly npm downloads and ended with a staggering 70,713,031 weekly downloads—a 65% increase in just twelve months. By the end of the year, ESLint had reached 2,964,923,725 total downloads for 2025 alone, a testament to the critical role it plays in the modern web development ecosystem.

Note: The dips downloads at the start and end of the year are regular seasonal declines that all packages see during the holidays.

Downloads for the v9.x release line continue to grow as the ecosystem upgrades from v8.x. By the end of 2025 and beginning of 2026, weekly downloads for the v9.x release line topped 36 million, more than half of our weekly downloads. The v8.x release line is still popular with over 26 million weekly downloads.

Integrating with AI

As AI became an integral part of the development workflow in 2025, we worked to ensure that ESLint remains a key part of that experience. In November, GitHub announced that ESLint is now integrated with Copilot code review in public preview. This integration allows Copilot to surface ESLint violations directly during the code review process, helping developers catch issues before they are merged.

We also embraced the Model Context Protocol (MCP) by releasing the @eslint/mcp package. This MCP server allows AI models, such as those used in VS Code’s Copilot, to interact directly with ESLint. By providing the AI with direct access to linting results and the ability to run ESLint on demand, we’re helping these tools provide more accurate and context-aware suggestions for your codebase.

Performance and workflow improvements

One of the most significant technical achievements of 2025 was the introduction of multithreaded linting in v9.34.0. This feature, which had been in discussion for over a decade, allows ESLint to utilize multiple CPU cores to lint files in parallel. Large projects have seen performance improvements ranging from 30% to over 300%, depending on the hardware and project structure.

We also introduced bulk suppressions in April. This feature allows teams to adopt stricter linting rules incrementally by marking existing violations for later fixing without cluttering the source code with comments. It has become a key tool for large-scale migrations and maintaining code quality in professional environments.

Updates to support the latest ECMAScript features

Keeping pace with the JavaScript language remains a core priority. In 2025, we added support for the following new JavaScript features:

• ES2026 Explicit Resource Management (using declarations)
• ES2025 Regex modifiers (completed rollout)
• ES2025 Global variables (Float16Array and Iterator)

These updates ensure that ESLint remains an up-to-date tool for modern JavaScript development.

The road to ESLint v10.0.0

The end of 2025 was focused on the next major milestone: ESLint v10.0.0. This release represents a significant cleanup of the project, including:

• Dropping support for Node.js < 20.19.0, allowing us to take advantage of modern Node.js features like native ESM support in require().
• Full removal of the legacy eslintrc configuration system, finalizing the transition to flat config that began years ago.
• Improving JSX reference tracking, making scope analysis more accurate for modern React and SolidJS applications.

We released the first alpha in November, followed by a beta in December, and we are currently in the release candidate phase as we head into 2026.

Financials review

The next few sections dig into the project financials. All of this information is gathered from the Open Collective transaction list with the exception of Tidelift payments (which are retrieved from Tidelift directly). Our fiscal 2025 runs from January 1, 2025 at midnight UTC to December 31, 2025 at 11:59 p.m. UTC.

Income review

During 2025, ESLint received $204,451.97 USD from all of our income sources. You can see the breakdown of our income sources in the following table.

We are pleased to see continued growth in our primary sponsorship channels via Open Collective and GitHub Sponsors. However, we saw a continued decline in Tidelift revenue and a significant drop in website ad revenue as we moved entirely to Ethical Ads.

Thanks.dev revenue actually increased to $11,337.61. This is a clerical issue because we forgot to cash out before the end of 2025 so $9,875.87 was received after the transaction deadline for our financials. Because we didn’t use this money to pay for expenses in 2025, we didn’t include it in the table.

Top sponsors

In 2025, we received generous donations from many companies, led by Automattic and Airbnb ($24,000 each), Meta Open Source ($20,000), and AG Grid ($20,000).

Expenses review

In 2025, we spent $262,150.09 USD on the ESLint project as a whole vs. $204,451.97 of income for a net loss of -$57,698.12. This is slightly better than our $59,705.24 loss in 2024, but it still reflects our active investment of our reserves into the project’s future.

Our Maintenance and Development costs continued to rise as we welcome four new team members, maintained three language plugins, tackled the core rewrite and the preparation for v10.0.0. We also significantly increased our investment in the Contributor Pool, which compensates outside contributors for high-impact work. We were able to offset some of these increases with lower costs for triage and community management compared to 2024.

Supporting our dependencies and ecosystem

As part of our commitment to the financial health of the JavaScript ecosystem, we continued to donate to the projects we depend on. In 2025, we increased our total donations to $16,500.00.

Looking forward to 2026

With ESLint v10.0.0 just around the corner, 2026 is shaping up to be another landmark year. Once v10.0.0 is stable, our primary focus will shift towards:

• Completing the Core Rewrite: Moving the remainder of the legacy core logic into the new language-agnostic architecture and making the core asynchronous.
• Expanding Language Plugins: Further improving CSS, JSON, and Markdown support, and exploring official plugins for other common web formats.
• Performance Optimization: Continuing to refine multithreaded linting and looking for further opportunities to reduce linting times.
• Cross-file Linting: Allow ESLint to follow dependencies through the files that it’s linting for more accurate results.

We are incredibly grateful to our community and sponsors for their continued support. Your contributions allow us to maintain ESLint as a high-quality, free, and open-source tool for millions of developers. We look forward to another year of growing and improving together!

Original source Report a problem

We just pushed ESLint v10.0.0-rc.0, which is a major release upgrade of ESLint. This release adds some new features and fixes several bugs found in the previous release. This release also has some breaking changes, so please read the following closely.

Highlights

This version of ESLint is not ready for production use and is provided to gather feedback from the community before releasing the final version. Please let us know if you have any problems or feedback by creating issues on our GitHub repo.

Note that this prerelease version of ESLint has a separate documentation section.

Enhancements to RuleTester

Since its earliest days, ESLint has provided the RuleTester API to help plugin authors test their rules against custom test cases and configurations. This release introduces several enhancements to RuleTester to enforce more robust test definitions and improve debugging.

requireData assertion option

A new assertion option, requireData, is now available. When set to true, RuleTester will require invalid test cases to include a data object whenever a messageId references a message with placeholders. This helps ensure that tests remain consistent with rule messages that rely on placeholder substitution.

For example, consider a hypothetical rule no-trivial-sum that reports on expressions such as 1 + 2 and defines a message with placeholders:

trivialSum: "Trivial sum found. Replace {{actualExpression}} with {{sum}}."

If an invalid test case includes messageId: "trivialSum" but omits data:

assertionOptions: { requireData: true }, invalid: [ { code: "const a = 1 + 2;", errors: [ { messageId: "trivialSum" } ] } ]

RuleTester will now throw an assertion error indicating that the data property is missing.

To resolve this, include the placeholder values in the error object:

{ code: "const a = 1 + 2;", errors: [ { messageId: "trivialSum", data: { actualExpression: "1 + 2", sum: 3 } } ] }

Improved location reporting for failing tests

RuleTester now decorates stack traces with information that makes it easier to locate failing test cases in your source code. For example, if the no-trivial-sum rule fails to report an error for 1 + 2, the test case in the previous section will fail and the test output will include stack trace lines like:

roughly at RuleTester.run.invalid[0] (/my-project/test/no-trivial-sum.js:10)
roughly at RuleTester.run.invalid (/my-project/test/no-trivial-sum.js:7)

The first line indicates:
• invalid[0]: the index of the failing test case in the invalid array
• /my-project/test/no-trivial-sum.js:10: the file and line number where that test case is defined. Many IDE terminals, including Visual Studio Code’s, recognize this format and allow you to click directly to the relevant line.

The second line points to the start of the entire invalid array.

Note that these line numbers may not always be included, depending on how your tests are structured. When the lines cannot be determined precisely, the failing test index (e.g., 0) and the printed code snippet are still available to locate the test case.

countThis option in max-params rule

The max-params rule now supports the new countThis option, which supersedes the deprecated countVoidThis. With the setting countThis: "never", the rule will now ignore any this annotation in a function’s argument list when counting the number of parameters in a TypeScript function. For example:

function doSomething(this: SomeType, first: string, second: number) {
  // ...
}

will be considered a function taking only 2 parameters.

Installing

Since this is a pre-release version, you will not automatically be upgraded by npm. You must specify the next tag when installing:

npm i eslint@next --save-dev

You can also specify the version directly:

npm i [email protected] --save-dev

Migration Guide

As there are a lot of changes, we’ve created a migration guide describing the breaking changes in great detail along with the steps you should take to address them. We expect that most users should be able to upgrade without any build changes, but the migration guide should be a useful resource if you encounter problems.

Breaking Changes

• feat!: estimate rule-tester failure location ( #20420 ) (ST-DDT)

Features

• feat: rule tester add assertion option requireData ( #20409 ) (fnx)
• feat: output RuleTester test case failure index ( #19976 ) (ST-DDT)
• feat: add countThis option to max-params ( #20236 ) (Gerkin)

Bug Fixes

• fix: update eslint ( #20427 ) (renovate[bot])
• fix: error location should not modify error message in RuleTester ( #20421 ) (Milos Djermanovic)
• fix: ensure filename is passed as third argument to verifyAndFix() ( #20405 ) (루밀LuMir)
• fix: remove ecmaVersion and sourceType from ParserOptions type ( #20415 ) (Pixel998)
• fix: remove TDZ scope type ( #20231 ) (jaymarvelz)
• fix: correct Scope typings ( #20404 ) (sethamus)
• fix: update verify and verifyAndFix types ( #20384 ) (Francesco Trotta)

Documentation

• docs: Update README (GitHub Actions Bot)
• docs: [no-await-in-loop] Expand inapplicability ( #20363 ) (Niklas Hambüchen)
• docs: Update README (GitHub Actions Bot)
• docs: update config syntax in no-lone-blocks ( #20413 ) (Pixel998)
• docs: remove redundant sourceType: "module" from rule examples ( #20412 ) (Pixel998)
• docs: correct .mts glob pattern in files with extensions example ( #20403 ) (Ali Essalihi)

Chores

• chore: package.json update for @eslint/js release (Jenkins)
• refactor: remove raw parser option from JS language ( #20416 ) (Pixel998)
• chore: remove category from type test fixtures ( #20417 ) (Pixel998)
• chore: remove category from formatter test fixtures ( #20418 ) (Pixel998)
• chore: add JSX language tag validation to check-rule-examples ( #20414 ) (Pixel998)
• chore: pin dependencies ( #20397 ) (renovate[bot])
• test: replace deprecated rules in linter tests ( #20406 ) (루밀LuMir)
• test: enable strict mode in type tests ( #20398 ) (루밀LuMir)
• refactor: remove lib/linter/rules.js ( #20399 ) (Francesco Trotta)
• chore: updates for v9.39.2 release (Jenkins)

Original source Report a problem

Highlights

This version of ESLint is not ready for production use and is provided to gather feedback from the community before releasing the final version. Please let us know if you have any problems or feedback by creating issues on our GitHub repo.

Most of the highlights of this release are breaking changes, and are discussed further in the migration guide. There are summaries of the significant changes below. (Less significant changes are included in the migration guide.)

This prerelease version of ESLint has a separate documentation section.

RuleTester assertion options

The RuleTester#run() method now supports assertion options, specifically requireMessage and requireLocation, to let developers enforce stricter requirements in rule tests. These options enforce that every invalid test case explicitly checks violation messages and/or locations, ensuring that a test fails if it doesn’t meet the requirements.

• requireMessage
  • Ensures every test case includes a message check.
  • Accepts:
    • true: Must use an array of objects for errors, rather than a numeric count shorthand, to check the problems reported by a rule. Each object must include a message or messageId property as usual to check the message of a reported problem.
    • "message": Must check using message only.
    • "messageId": Must check using messageId only.
  • Purpose: Prevents tests from passing without verifying the actual message.
• requireLocation
  • Ensures every test case includes a location check.
  • Accepts:
    • true
  • Requires line and column in each object of the errors array.
  • endLine and endColumn are optional if the actual report doesn’t include them.
  • Purpose: Guarantees that tests validate the location of an error.

Example Usage:

ruleTester.run("my-rule", rule, {
  valid: [
    { code: "var foo = true;" }
  ],
  invalid: [
    {
      code: "var invalidVariable = true;",
      errors: [
        { message: "Unexpected invalid variable.", line: 1, column: 5 }
      ]
    }
  ],
  assertionOptions: {
    requireMessage: true,
    requireLocation: true
  }
});

Here, the test must include both a message check and location check for each error.

JSX references are now tracked

ESLint v10.0.0 now tracks JSX references, enabling correct scope analysis of JSX elements.

Previously, JSX identifiers weren’t tracked as references, which could lead to incorrect results in rules relying on scope information. For example:

import { Card } from "./card.jsx";
export function createCard(name) {
  return <Card name={name} />;
}

Prior to v10.0.0:

• False positives: could be reported as “defined but never used” (no-unused-vars).
• False negatives: Removing the import might not trigger an “undefined variable” error (no-undef).

Starting with v10.0.0, is treated as a normal reference to the variable in scope. This eliminates confusing false positives/negatives, aligns JSX handling with developer expectations, and improves the linting experience in projects using JSX.

If your codebase includes JSX, you may start seeing new linting reports. To fix them, update your code or adjust rule configurations as needed.

color property in formatter context

When the --color or --no-color option is specified on the command line, ESLint sets an additional color property on the context object passed to a formatter (the second argument of the format() method). This property is true for --color and false for --no-color. Custom formatters can use this value to determine whether to apply color styling, based on the assumption that the terminal supports or does not support colors as indicated by the option.

For the default “stylish” formatter, the --color or --no-color option now takes precedence over other rules checked by Node.js (such as the environment variables FORCE_COLOR, NODE_DISABLE_COLORS, etc.) when deciding whether to apply colorization.

Installing

Since this is a pre-release version, you will not automatically be upgraded by npm. You must specify the next tag when installing:

npm i eslint@next --save-dev

You can also specify the version directly:

npm i [email protected] --save-dev

Migration Guide

As there are a lot of changes, we’ve created a migration guide describing the breaking changes in great detail along with the steps you should take to address them. We expect that most users should be able to upgrade without any build changes, but the migration guide should be a useful resource if you encounter problems.

Breaking Changes

• a176319 feat!: replace chalk with styleText and add color to ResultsMeta (#20227) (루밀LuMir)
• c7046e6 feat!: enable JSX reference tracking (#20152) (Pixel998)

Features

• f148a5e feat: add error assertion options (#20247) (ST-DDT)

Bug Fixes

• ba6ebfa fix: correct typings for loadESLint() and shouldUseFlatConfig() (#20393) (루밀LuMir)
• e7673ae fix: correct RuleTester typings (#20105) (Pixel998)
• 53e9522 fix: strict removed formatters check (#20241) (ntnyq)
• b017f09 fix: correct no-restricted-import messages (#20374) (Francesco Trotta)

Documentation

• 264b981 docs: Update README (GitHub Actions Bot)
• 5a4324f docs: clarify "local" option of no-unused-vars (#20385) (Milos Djermanovic)
• e593aa0 docs: improve clarity, grammar, and wording in documentation site README (#20370) (Aditya)
• 3f5062e docs: Add messages property to rule meta documentation (#20361) (Sabya Sachi)
• 9e5a5c2 docs: remove Examples headings from rule docs (#20364) (Milos Djermanovic)
• 194f488 docs: Update README (GitHub Actions Bot)

Build Related

• a126a2a build: add .scss files entry to knip (#20389) (Francesco Trotta)

Chores

• 54bf0a3 ci: create package manager test (#20392) (루밀LuMir)
• 3115021 refactor: simplify JSDoc comment detection logic (#20360) (Pixel998)
• 4345b17 chore: update @eslint-community/regexpp to 4.12.2 (#20366) (루밀LuMir)
• 772c9ee chore: update dependency @eslint/eslintrc to ^3.3.3 (#20359) (renovate[bot])

Original source Report a problem

We just pushed ESLint v9.39.2, which is a patch release upgrade of ESLint. This release fixes several bugs found in the previous release.

Highlights

This release prints a warning message when an /* eslint-env / configuration comment is found in the code being linted. The warning includes the filename and line number of the comment, along with instructions on how to replace it. The purpose of this warning is to allow for a smoother migration, since starting with ESLint v10.0.0, / eslint-env */ comments are reported as errors by the linter, as explained in the migration guide.

Bug Fixes

• fix: warn when eslint-env configuration comments are found (#20381) (sethamus)

Build Related

• build: add .scss files entry to knip (#20391) (Milos Djermanovic)

Chores

• chore: upgrade to @eslint/[email protected] (#20394) (Francesco Trotta)
• chore: package.json update for @eslint/js release (Jenkins)
• ci: add v9.x-dev branch (#20382) (Milos Djermanovic)

Original source Report a problem

Highlights

This version of ESLint is not ready for production use and is provided to gather feedback from the community before releasing the final version. Please let us know if you having any problems or feedback by creating issues on our GitHub repo.

Most of the highlights of this release are breaking changes, and are discussed further in the migration guide. There are summaries of the significant changes below. (Less significant changes are included in the migration guide.)

This prerelease version of ESLint has a separate documentation section.

Removed deprecated SourceCode methods

The following SourceCode methods are no longer available:

• getTokenOrCommentBefore() - Use getTokenBefore() with the { includeComments: true } option instead
• getTokenOrCommentAfter() - Use getTokenAfter() With the { includeComments: true } option instead
• isSpaceBetweenTokens() - Use isSpaceBetween() instead
• getJSDocComment() - No replacement

Users of plugins that haven’t updated their code yet can use the @eslint/compat utility in the meantime.

Installing

Since this is a pre-release version, you will not automatically be upgraded by npm. You must specify the next tag when installing:

npm i eslint@next --save-dev

You can also specify the version directly:

npm i [email protected] --save-dev

Migration Guide

As there are a lot of changes, we’ve created a migration guide describing the breaking changes in great detail along with the steps you should take to address them. We expect that most users should be able to upgrade without any build changes, but the migration guide should be a useful resource if you encounter problems.

Breaking Changes

• fa31a60 feat!: add name to configs (#20015) (Kirk Waiblinger)
• 3383e7e fix!: remove deprecated SourceCode methods (#20137) (Pixel998)
• 501abd0 feat!: update dependency minimatch to v10 (#20246) (renovate[bot])
• ca4d3b4 fix!: stricter rule tester assertions for valid test cases (#20125) (唯然)

Features

• 09e6654 feat: update error loc of require-yield and no-useless-constructor (#20267) (Tanuj Kanti)

Documentation

• 0f5a94a docs: [class-methods-use-this] explain purpose of rule (#20008) (Kirk Waiblinger)
• df5566f docs: add Options section to all rule docs (#20296) (sethamus)
• adf7a2b docs: no-unsafe-finally note for generator functions (#20330) (Tom Pereira)
• ef7028c docs: Update README (GitHub Actions Bot)
• fbae5d1 docs: consistently use “v10.0.0” in migration guide (#20328) (Pixel998)
• 778aa2d docs: ignoring default file patterns (#20312) (Tanuj Kanti)

Chores

• 0b14059 chore: package.json update for @eslint/js release (Jenkins)
• d6e7bf3 ci: bump actions/checkout from 5 to 6 (#20350) (dependabot[bot])
• 139d456 chore: require mandatory headers in rule docs (#20347) (Milos Djermanovic)
• 3b0289c chore: remove unused .eslintignore and test fixtures (#20316) (Pixel998)
• a463e7b chore: update dependency js-yaml to v4 [security] (#20319) (renovate[bot])
• ebfe905 chore: remove redundant rules from eslint-config-eslint (#20327) (Milos Djermanovic)
• 88dfdb2 test: add regression tests for message placeholder interpolation (#20318) (fnx)
• 6ed0f75 chore: skip type checking in eslint-config-eslint (#20323) (Francesco Trotta)

Original source Report a problem