FASTJSON

Health v2 · maintenance only

Adoption not part of the score

4397 stars · 603 forks observed · 2026-08-28

What it is AI-extracted, prompt v1, taxonomy v1, 2026-08-29, confidence not recorded

Fast is a high-performance Java JSON library for converting Java objects to JSON and back, working with arbitrary Java objects including pre-existing unmodifiable classes. Fast 2.0 is the actively maintained successor with better performance, security (autoType whitelist removed), GraalVM and Kotlin support.

Use cases

• serialize java objects to
• parse strings into java objects
• fast parsing on android
• convert to pojo without source code
• serialization for rpc payloads
• handle deeply nested generic structures

When to choose

• you need maximum JSON throughput on the JVM or Android
• you must serialize pre-existing classes you cannot modify
• you want a mature, widely used Java JSON library
• you need fast 1.x compatibility via fast2 compat mode

When to avoid

• you prefer a standards-based API like Jackson or Jakarta JSON Binding
• you need cross-language JSON support beyond the JVM
• you are starting a new project and want the most mainstream ecosystem choice

Facets

library · maturity stable

serialization parser developer-tools backend apis jvm -parser -serialization deserialization high-performance alibaba android

Member repositories

For agents

markdown · JSON · MCP: product_card(name="alibaba/fastjson2")