Best API Development Tools Open Source Tools in 2026

Airbyte

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

Open source ELT platform with 300+ data connectors

stars 21.1Klicense NOASSERTIONlang Python

Developer Tools API Infrastructure Database+14

Metarank

AI & Machine Learning Data & Analytics Web & App Development

Open source personalization and search ranking engine

stars 2.4Klicense Apache-2.0lang Scala

Search Engine LLM A/B Testing+10

Sylius

Web & App Development IT Management Product & Project Management

Headless Symfony commerce for complex B2B and B2C stores

stars 8.5Klicense MITlang PHP

Developer Tools Developer Framework API Development Tools+11

Totum

Web & App Development Business & Productivity IT Management+2

Self-hosted low-code platform for internal business tools

stars 983license MITlang PHP

Database No Code Self Hosted+11

BigchainDB

Data & Analytics Web & App Development Finance & Fintech+1

Blockchain database with high throughput and low latency

stars 4Klicense Apache-2.0lang Python

Database Web3 Authentication+5

Bagisto

Web & App Development Product & Project Management Business & Productivity

Laravel eCommerce with headless API and no transaction fees

stars 26.6Klicense MITlang PHP

Marketplace Developer Framework API Development Tools+6

Apache CouchDB

Web & App Development Data & Analytics IT Management

NoSQL database with multi-primary sync and HTTP API

stars 6.9Klicense Apache-2.0lang Erlang

Database No Code API Development Tools+3

DocuSeal

Web & App Development Business & Productivity Finance & Fintech

Open source document signing and fillable PDF forms

stars 11.8Klicense AGPL-3.0lang Ruby

Developer Tools API Development Tools Workflow Automation+12

PouchDB

Web & App Development Data & Analytics Business & Productivity

JavaScript database that syncs with CouchDB, works offline

stars 17.6Klicense Apache-2.0lang JavaScript

Database Developer Tools API Development Tools+1

UVdesk

Customer Support Business & Productivity Web & App Development

Helpdesk and ticketing on PHP/Symfony with workflow automation

stars 18.5Klicense OSL-3.0lang CSS

Customer Support Knowledge Base Workflow Automation+7

ProjectDiscovery

Security & Monitoring Web & App Development IT Management+1

Open source security tools for finding vulnerabilities at scale

stars 28.1Klicense MITlang Go

Developer Tools DevOps Tools Cybersecurity+18

Temporal

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

Durable workflow orchestration for reliable, long-running apps

stars 19.9Klicense MITlang Go

Workflow Orchestration Developer Framework Developer Tools+14

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Airbyte

Metarank

Sylius

Totum

BigchainDB

Bagisto

Apache CouchDB

DocuSeal

PouchDB

UVdesk

ProjectDiscovery

Temporal

Airbyte

Metarank

Sylius

Totum

BigchainDB

Bagisto