Dev tools · alternatives · 2026

24 alternatives to Testnizer — The offline API client

Offline, open-source API client. Your data never leaves.

Below are 24 products that do a similar job, ranked by how close each is in meaning and then by launch-day votes.

1. 1
   Free Monitoring Suite by WebGazer▲338

   Monitoring for websites, APIs, and cron jobs

   2024 · webgazer.io · its alternatives →

2. 2
   Restfox – Open source lightweight alternative to Postman▲758

   Last time I posted this it didn't garner much interest. There have been lots of improvements and fixes since the last release. Quick list of features: - Workspaces - Tabs - Nested Folders - Lots of context menus - Response history - Plugins - Runs fully in the browser and runs offline if necessary - Chrome and Firefox extension to bypass CORS restrictions - Desktop builds for all platforms - GraphQL support - Import collections exported from Postman and Insomnia - Simple user friendly interface I built this because I love Insomnia but wanted a portable version that I could run in the…

   2022 · restfox.dev · its alternatives →

3. 3
   Voiden API Client▲143

   Hey HN! Aldin here, a helping hand to Voiden (https://voiden.md) Voiden is a free, offline, Git-native API client. Your API definitions, docs, and tests all live together. It came out of years of frustration: cloud sync lock-in, paywalled basics, bloated UIs, and lag on even simple requests. So the team built the opposite: an offline tool with no login, no telemetry, no lock-in. Just markdown and hotkeys. It behaves like code: local files, git branches, no cloud nonsense. Terminal is built-in, so you can commit, diff, and push changes right from the app. Docs stay close to your…

   2025 · voiden.md · its alternatives →

4. 4
   Sparrow▲456

   The lightest and fastest platform for API testing

   2025 · sparrowapp.dev · its alternatives →

5. 5
   Apicat – A Lightweight Offline Postman Alternative▲13

   Apicat is the ultimate offline Postman alternative that stores your .http files locally. It’s Git-friendly, open-source, and highly compatible with Postman. Test APIs offline with this powerful free offline API client designed for developers who need a reliable local API testing tool.

   2025 · apicat.com · its alternatives →

6. 6
   Cursor for your API▲473

   Generate, edit, lint & test your API workflow in one place

   2025 · app.getelva.ai · its alternatives →

7. 7
   DevUtils▲197

   Developer utilities for macOS

   2020 · devutils.com · its alternatives →

8. 8MS
   Mocktastic – Simple, Offline mock REST APIs for your entire team▲43

   2018 · mocktastic.com · its alternatives →

9. 9
   HTTP Mock – Intercept, debug and mock HTTP(S) with zero setup▲341

   Beautiful, cross-platform & open-source tools for debugging, testing and building with HTTP(S), on Windows, Linux & Mac.

   2019 · httptoolkit.tech · its alternatives →

10. 10
    Insomnia REST Client now open-source▲218

    Leading Open Source API Development Platform for HTTP, REST, GraphQL, gRPC, SOAP, and WebSockets

    2017 · insomnia.rest · its alternatives →

11. 11
    Akto's Test Editor▲143

    Your playground for writing custom API security tests

    2023 · akto.io · its alternatives →

12. 12
    HawkClient▲7

    Git friendly, offline-only API testing tool

    Nov 2025 · hawkclient.com · its alternatives →

13. 13
    Deposure▲185

    Launch your APIs live effortlessly

    2025 · its alternatives →

14. 14
    ApiHome▲73

    Home of API testing

    2022 · apihome.io · its alternatives →

15. 15
    DevHub▲126

    Offline applications to support developers' daily tasks

    2024 · apps.apple.com · its alternatives →

16. 16
    Easy Serverless GraphQL APIs with Serverless Framework AppSync▲90

    2019 · github.com · its alternatives →

17. 17
    Karate Labs▲115

    Open-source platform unifying API & UI test automation

    2023 · karatelabs.io · its alternatives →

18. 18
    Resterm – A terminal-based REST/GraphQL and gRPC client▲29

    Terminal API client for HTTP, GraphQL and gRPC. Plain .http files you can diff and version, with workflows, mocks, profiling, tracing, OpenAPI import, SSH tunnels, Kubernetes port-forwards, WebSocket, SSE and a CLI runner. - unkn0wn-root/resterm

    2025 · github.com · its alternatives →

19. 19
    Mockoon – mock REST APIs in seconds▲68

    Mockoon is the easiest and quickest way to run mock REST API servers. No remote deployment, no account required, free, open source and cross-platform.

    2017 · mockoon.com · its alternatives →

20. 20
    Karate▲89

    Web-services testing made simple 🥋

    2018 · github.com · its alternatives →

21. 21
    Voiden – an offline, Git-native API tool built around Markdown▲48

    Hi HN, We have open-sourced Voiden. Most API tools are built like platforms. They are heavy because they optimize for accounts, sync, and abstraction - not for simple, local API work. Voiden treats API tooling as files. It’s an offline-first, Git-native API tool built on Markdown, where specs, tests, and docs live together as executable Markdown in your repo. Git is the source of truth. No cloud. No syncing. No accounts. No telemetry.Just Markdown, Git, hotkeys, and your damn specs. Voiden is extensible via plugins (including gRPC and WSS). Repo:…

    Feb 2026 · github.com · its alternatives →

22. 22
    GraphQL Client in the Terminal▲64

    Build and execute GraphQL queries in the terminal. - eerimoq/gqt

    2022 · github.com · its alternatives →

23. 23
    Upyng Go - DevTools & More▲7

    Your Ultimate Offline Toolkit

    2025 · apps.apple.com · its alternatives →

24. 24
    Rust built open-sourced CLI tool for API specification validation▲23

    Stop half-done APIs! Cherrybomb is a CLI tool that helps you avoid undefined user behaviour by auditing your API specifications, validating them and running API security tests. - blst-security/cherrybomb

    2022 · github.com · its alternatives →

Ranked by how close each launch is in meaning, then by votes. Prices were read from each product’s own site when checked and can change. Refine with your own description →