com-lihaoyi/fastparse

Health v2 · maintenance only

Adoption not part of the score

1135 stars · 164 forks observed · 2026-08-28

What it is AI-extracted, prompt v1, taxonomy v1, 2026-08-30, confidence not recorded

FastParse is a Scala parser-combinator library for parsing strings and bytes into structured data, with hand-written-parser-level speed and excellent error reporting. It works on both Scala JVM and Scala.js and includes example parsers for Scala, Python, and CSS.

Use cases

• parse custom text file formats in Scala
• build a parser for a programming language or DSL
• parse JSON-like structured data with good error messages
• write fast parser combinators instead of regex hacks
• parse source code in the browser via Scala.js
• stream-parse large datasets without loading everything into memory

When to choose

• you need a fast, maintainable parser in Scala with great diagnostics
• you want parser combinators far faster than scala-parser-combinators
• you need parsing on both JVM and JavaScript via Scala.js

When to avoid

• you need a parser generator producing standalone grammars like ANTLR
• you are not working in Scala or a JVM/Scala.js ecosystem
• you need extreme-performance binary parsing beyond combinator overhead

Facets

library · maturity stable

parser parsers programming-languages developer-tools jvm browser cross-platform parser-combinators scala-js scala error-reporting text-parsing

Member repositories

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