Best Open Source API Clients using Testing Library in 2026

Bruno

Lightweight, fast, and open-source API client for developers

Stars
43,158
Forks
2,329
Last commit
5 hours ago

A modern, user-friendly API client that simplifies API testing and development with a clean interface and powerful features.

Open Source Alternative to:

Postman

Insomnia

Powerful API development and testing made effortless

Stars
38,335
Forks
2,280
Last commit
4 hours ago

Intuitive API client for REST, GraphQL, and gRPC. Debug, test, and collaborate on APIs with ease across platforms.

Open Source Alternative to:

Postman

Firecamp

Unified API development ecosystem for modern teams

Stars
2,589
Forks
166
Last commit
2 months ago

All-in-one platform for API testing, documentation, and collaboration, simplifying the entire API development lifecycle.

Open Source Alternative to:

Postman

Voiden

Build APIs like code with Git-native workspace

Stars
827
Forks
25
Last commit
7 hours ago

Offline-first API workspace that unifies specs, docs, tests, and mocks in programmable Markdown blocks. Version control everything in plain text files.

Open Source Alternative to:

Postman

Stars
Forks
Last commit

Stars
Forks
Last commit

Stars
Forks
Last commit

Stars
Forks
Last commit

Stars
Forks
Last commit

Stars
Forks
Last commit

Bruno

Lightweight, fast, and open-source API client for developers

Stars
43,158
Forks
2,329
Last commit
5 hours ago

A modern, user-friendly API client that simplifies API testing and development with a clean interface and powerful features.

Open Source Alternative to:

Postman

Insomnia

Powerful API development and testing made effortless

Stars
38,335
Forks
2,280
Last commit
4 hours ago

Intuitive API client for REST, GraphQL, and gRPC. Debug, test, and collaborate on APIs with ease across platforms.

Open Source Alternative to:

Postman

Firecamp

Unified API development ecosystem for modern teams

Stars
2,589
Forks
166
Last commit
2 months ago

All-in-one platform for API testing, documentation, and collaboration, simplifying the entire API development lifecycle.

Open Source Alternative to:

Postman

Voiden

Build APIs like code with Git-native workspace

Stars
827
Forks
25
Last commit
7 hours ago

Offline-first API workspace that unifies specs, docs, tests, and mocks in programmable Markdown blocks. Version control everything in plain text files.

Open Source Alternative to:

Postman

Open Source API Clients using Testing Library

A curated collection of the best open source client applications for interacting with and testing APIs. using Testing Library.