Best API Development Tools Open Source Tools in 2026

pdftk-java

Web & App Development

Java port of PDFtk for merging, splitting, and stamping PDFs

stars 2.2Klicense NOASSERTIONlang HTML

Developer Tools Coding AI Coding Assistant+2

Ghostscript

Web & App Development IT Management

Open source PDF and PostScript interpreter and converter

stars 224license NOASSERTIONlang C

Developer Tools API Development Tools Coding+4

Meilisearch

Web & App Development AI & Machine Learning Data & Analytics+1

Typo-tolerant search engine with instant results, one binary

stars 57.3Klicense NOASSERTIONlang Rust

Search Engine Open Core Developer Tools+12

Typesense

Web & App Development AI & Machine Learning Data & Analytics+1

Fast typo-tolerant search engine with instant results

stars 555license Apache-2.0lang TypeScript

Search Engine Open Core Developer Tools+12

Fusio

Web & App Development IT Management Business & Productivity+1

Build, document, and monetize APIs from one self-hosted platform

stars 2.1Klicense Apache-2.0lang PHP

API Infrastructure API Development Tools Developer Tools+5

Codegen

Web & App Development AI & Machine Learning Business & Productivity+2

AI that reviews your code, fixes bugs, and implements features

stars 521license Apache-2.0lang Python

AI Coding Assistant AI Agents Coding+16

inlang

Web & App Development

Open source localization ecosystem for software teams

stars 1.9Klang TypeScript

Developer Tools Coding Code Editors+3

Cube

Data & Analytics AI & Machine Learning Web & App Development

Headless BI platform with a shared semantic layer for your data

stars 19.9Klicense NOASSERTIONlang Rust

API Infrastructure Data Visualization Web Analytics+5

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pdftk-java

Ghostscript

Meilisearch

Typesense

Fusio

Codegen

inlang

Cube

pdftk-java

Ghostscript

Meilisearch

Typesense

Fusio

Codegen

inlang

Cube