Best API Development Tools Open Source Tools in 2026

Better Auth

Backend Development Security & Monitoring Developer Tools

Drop-in TypeScript auth with MFA, SSO, and multi-tenancy support

stars 28.3Klicense MITlang TypeScript

Authentication Self Hosted Developer Framework+4

Yaak

Developer Tools APIs & Integration Web Development

Local-first API client for HTTP, GraphQL, and WebSocket

stars 18.6Klicense MITlang TypeScript

API Client API Development Tools Testing+3

Sylius

Web Development APIs & Integration Backend Development

Headless Symfony commerce for complex B2B and B2C stores

stars 8.5Klicense MITlang PHP

E-commerce Headless CMS Developer Framework+5

BigchainDB

Databases & Storage Web Development Finance & Fintech

Blockchain database with high throughput and low latency

stars 4Klicense Apache-2.0lang Python

Database Web3 API Development Tools+4

Bagisto

Web Development Business & Productivity APIs & Integration

Laravel eCommerce with headless API and no transaction fees

stars 26.8Klicense MITlang PHP

E-commerce Marketplace Developer Framework+4

Saleor

Web Development APIs & Integration Backend Development

Open source headless e-commerce platform with GraphQL API

stars 22.9Klicense BSD-3-Clauselang Python

E-commerce Headless CMS API Development Tools+5

PouchDB

Databases & Storage Web Development Developer Tools

JavaScript database that syncs with CouchDB, works offline

stars 17.6Klicense Apache-2.0lang JavaScript

Database Developer Framework API Development Tools+3

Sulu

Web Development Developer Tools Product & Project Management

Enterprise-ready open source CMS built on Symfony

stars 1.3Klicense MITlang PHP

CMS Headless CMS Developer Framework+4

Novu

Communication & Collaboration APIs & Integration Developer Tools

Open source notification infrastructure for product teams

stars 39Klicense NOASSERTIONlang TypeScript

API Infrastructure Developer Tools Email+5

DuckDB

Data & Analytics Databases & Storage Developer Tools

Fast in-process SQL analytics database, no server needed

stars 38.1Klicense MITlang C++

Database Developer Tools Coding+3

Directus

Web Development APIs & Integration Databases & Storage

Wrap any SQL database with REST and GraphQL APIs and an admin UI

stars 35.7Klicense NOASSERTIONlang TypeScript

Headless CMS API Development Tools API Infrastructure+5

TinaCMS

Web Development Product & Project Management Developer Tools

Open source headless CMS with inline editing and Git backend

stars 13.3Klicense Apache-2.0lang TypeScript

Headless CMS CMS Developer Tools+5

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Better Auth

Yaak

Sylius

BigchainDB

Bagisto

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PouchDB

Sulu

Novu

DuckDB

Directus

TinaCMS

Better Auth

Yaak

Sylius

BigchainDB

Bagisto

Saleor