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Open Source API Clients using CSS

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

Hoppscotch

Sleek, intuitive API development and testing platform

  • Stars

    80,660

  • Last commit

    7 hours ago

  • License

    MIT
Lightweight, fast, and feature-rich API client for developers. Test, debug, and document APIs with ease in a clean, modern interface.

Open Source Alternative to:

Postman

Bruno

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

  • Stars

    47,756

  • Last commit

    1 day ago

  • License

    MIT
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

    40,063

  • Last commit

    6 hours ago

  • License

    Apache-2.0
Intuitive API client for REST, GraphQL, and gRPC. Debug, test, and collaborate on APIs with ease across platforms.

Open Source Alternative to:

Postman

Yaak

Fast, secure, offline API client with Git integration

  • Stars

    19,338

  • Last commit

    1 day ago

  • License

    MIT
A modern API client offering local-only data storage, Git integration, plugin extensibility, and multi-protocol support for developers.

Open Source Alternative to:

Postman

Requestly

Intercept, modify, and debug HTTP(S) requests effortlessly

  • Stars

    6,754

  • Last commit

    1 day ago

  • License

    AGPL-3.0
A powerful browser extension and desktop app for developers to manipulate network requests, debug APIs, and improve web app testing

Open Source Alternative to:

Postman

Voiden

Build APIs like code with Git-native workspace

  • Stars

    Stars growing over the last 30 days1,869

  • Last commit

    1 day ago

  • License

    Apache-2.0
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

Firecamp

Unified API development ecosystem for modern teams

  • Stars

    2,618

  • Last commit

    8 months ago

  • License

    AGPL-3.0
All-in-one platform for API testing, documentation, and collaboration, simplifying the entire API development lifecycle.

Open Source Alternative to:

Postman
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