# Chevrotain/chevrotain

Parser Building Toolkit for JavaScript

Repository: https://github.com/Chevrotain/chevrotain
Canonical: https://ross.abutalabs.com/products/chevrotain
Homepage: https://chevrotain.io
Language: TypeScript
License: Apache-2.0
License Family: permissive
Topics: javascript, typescript, parser-library, parsing, grammars, tokenizer, open-source, lexer
Last push: 2026-08-25T20:43:49+00:00

## Health v2 (maintenance only)
Score: 67/100 (v2, computed 2026-09-03T02:20:16.233290+00:00)
- activity 99, release rhythm 8, longevity 100
- inputs: {"age_days": 4158, "days_push": 8, "days_rel": null, "gap_med": null, "n_releases_24m": 0}
- flags: none
- formula: round(0.45*activity + 0.35*rhythm + 0.20*longevity); archived -> min(score, 10)

## Adoption (not part of the score)
Stars 2797, forks 221 (observed 2026-08-28T04:07:22.444521+00:00)

## What it is
Chevrotain is a fast, feature-rich parser building toolkit for JavaScript with built-in LL(K) grammar support. Grammars are written as pure JavaScript/TypeScript source without a code generation phase, usable from simple config files to full programming languages.

## Use cases
- build a parser for a custom DSL in JavaScript
- write a lexer and tokenizer for a new language
- parse configuration files with a custom grammar
- build an interpreter or compiler frontend in TypeScript
- implement syntax highlighting by tokenizing source code
- replace parser generators with a no-codegen parsing library

## When to choose
- you need high-performance parsing in JavaScript or TypeScript
- you want grammars as plain code without a code generation build step
- you need fine control over lexer and parser error recovery

## When to avoid
- you prefer declarative grammar files with generated parsers (e.g., ANTLR)
- you need PEG or GLR parsing rather than LL(K)/LL(*)
- you are not working in a JavaScript runtime

## Facets
- artifact type: library
- maturity: stable
- function: parser, compiler, developer-tools
- domain: parsers, programming-languages, developer-tools
- platform: browser
- tags: lexer, tokenizer, ll-k, grammar, dsl, syntax-analysis, no-code-generation, nodejs, javascript, typescript

## Member repositories
- Chevrotain/chevrotain (main) score 67

## Provenance
- Observed fields: from GitHub, fetched 2026-08-28T04:07:22.444521+00:00.
- Health v2: computed from the inputs above; adoption is never an input.
- Inferred fields (summary, facets, guidance): AI-extracted, prompt v1, taxonomy v1, on 2026-08-30T08:14:39.070984+00:00, confidence not recorded.
  - readme: https://github.com/Chevrotain/chevrotain (fetched 2026-08-28T04:07:22.444521+00:00, sha 20806ae2434e)
  - homepage: https://chevrotain.io (fetched 2026-08-29T09:55:04.494612+00:00, sha 44136fa355b3)
- Data as of 2026-08-30T08:39:29.467469+00:00.