Acorn is a small, fast JavaScript-based JavaScript parser, written entirely in JavaScript, useful for parsing JavaScript code in developer tools and tooling. It also provides related packages like an error-tolerant parser (acorn-loose) and a syntax tree walker (acorn-walk), and supports plugin-based extensions to adjust parsing behavior for different JavaScript dialects.
Project status
- Actively maintained: GitHub shows recent upstream activity (last push 2026-04-30), and versioned updates (8.16.0 on 2026-02-19) indicate ongoing development rather than maintenance mode.
- Update cadence: The most recent tagged updates are spaced about 8 to 9 months apart (8.14.1 on 2025-03-05, 8.15.0 on 2025-06-08, 8.16.0 on 2026-02-19).
AI summary generated Today
Recent updates
8.16.0
3 months agoNo release notes were provided for version 8.16.0, so there is nothing explicitly documented by the publisher. The code diff indicates functional parser behavior changes (including support for `sourceType: "commonjs"`), updated contextual keyword handling, Unicode data updates, and some behavioral changes in `acorn-walk` error handling and import/export attribute traversal.
8.15.0
6/8/2025This release (8.15.0) introduces support for the ES2025 `using` and `await using` declaration syntax, plus related AST and parser updates. The publisher release notes section was empty, so most behavior and typing changes below are not documented there and need to be inferred from the code diff.
BreakingFeatures8.14.1
3/5/2025Release 8.14.1 was published on 2025-03-05, but no release notes or change details were provided by the publisher. As a result, there is no documented information available to assess new functionality, bug fixes, breaking changes, security updates, or dependency changes for this version.
8.14.0
10/27/2024No publisher release notes were provided for version 8.14.0, but the code changes are substantial. The update adds parsing support for ES2025 import attributes (including AST and TypeScript type updates), extends dynamic import() parsing with an optional second argument used as options, and adds support for ES2025 RegExp modifiers, along with Unicode data generation tweaks.
8.13.0
10/16/2024This release updates Acorn to version 8.13.0 and, importantly, refreshes the generated Unicode identifier data to Unicode 16.0.0. It also changes acorn-walk's traversal behavior for SwitchStatement cases, and bumps several development dependencies and the embedded test262 revision.
8.12.1
7/3/2024Release 8.12.1 is a small patch release with no publisher-provided release notes in the data provided. The code diff shows primarily a compatibility bug fix in Acorn's parsing utilities, plus build and CI/test configuration changes (Node setup action, rollup configs, and updated test262 commit and feature lists).
8.12.0
6/14/2024No GitHub release notes were provided for version 8.12.0. The code diff shows substantive changes to Acorn’s parser and RegExp validation, especially around ES2025 features (duplicate named capture groups) and improved error reporting and location tracking. Several TypeScript type definitions were also updated, and acorn-walk gained a new exported walker helper.
8.11.3
12/29/2023Release 8.11.3 has no publisher-provided release notes. The code diff shows a version bump and several bug fixes, plus a notable change in acorn-walk visitor callback invocation behavior and some TypeScript typing updates.
Breaking8.11.2
10/27/2023Acorn 8.11.2 is a small patch release (6 files changed, +13/-6 lines) focused on parsing/tokenization behavior. The provided publisher release notes are missing, so the only described change comes from the repo changelog and the actual code diff.
8.11.1
10/26/2023Release 8.11.1 was published on 2023-10-26, but the publisher provided no release notes. As a result, the changes, potential breaking behavior, bug fixes, and security or dependency updates are not documented here.