1. JSON Formatter
Makes raw JSON responses readable in the browser.
Why it replaces Rex — API Client: Covers similar ground in the Developer Tools category: Makes raw JSON responses readable in the browser.
Best Rex — API Client Alternatives in 2026
Rex — API Client is a strong option, but it is not the right fit for everyone. Below are 10 alternatives compared on rating, install base, pricing and the use case each one actually wins on.
About Rex — API Client
A fast, keyboard-driven REST API client for developers. Test APIs without leaving your browser.
Free
Full reviewComparison at a glance
| Extension | Rating | Users | Pricing | Best for |
|---|---|---|---|---|
| Rex — API Client (original) | — | — | Free | A fast, keyboard-driven REST API client for developers. Test APIs without leaving your browser. |
| JSON Formatter | 4.3 | 2M+ | Free | Anyone poking at REST APIs directly in the browser. |
| React Developer Tools | 3.9 | 5M+ | Free | React developers debugging component state and render performance. |
| Tag Assistant | 3.9 | 3M+ | Free | The Tag Assistant extension works with Tag Assistant to help troubleshoot installation of gtag.js and Google Tag Manager. |
| Wappalyzer | 4.6 | 3M+ | Freemium | Developers, agencies and sales teams researching what a site is built with. |
| Take Webpage Screenshots Entirely - FireShot | 4.8 | 3M+ | Free | Anyone who needs fast, reliable full-page screenshots for work, support or documentation. |
| Meta Ads Data Advisor | 3.9 | 3M+ | Free | Meta Ads Data Advisor automates connecting your website and marketing data to Meta for better ad performance. No developers needed. |
| Cookie-Editor | 4.4 | 2M+ | Free | Simple yet powerful Cookie Editor that allow you to quickly create, edit and delete cookies without leaving your tab. |
| Chromebook Recovery Utility | 2.6 | 2M+ | Free | Create recovery media for your Chromebook. |
| Web Developer | 4.5 | 1M+ | Free | Web developers who want quick access to common debugging tools without opening DevTools. |
| Lighthouse | 4.4 | 1M+ | Free | Lighthouse is an open-source, automated tool for improving the performance, quality, and correctness of your web apps. |
Rex — API Client alternatives in detail
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2. React Developer Tools
Inspect React component trees, props and state.
Why it replaces Rex — API Client: Another popular Developer Tools extension: Inspect React component trees, props and state.
3. Tag Assistant
The Tag Assistant extension works with Tag Assistant to help troubleshoot installation of gtag.js and Google Tag Manager.
Why it replaces Rex — API Client: Another popular Developer Tools extension: The Tag Assistant extension works with Tag Assistant to help troubleshoot installation of gtag.js and Google Tag Manager.
4. Wappalyzer
Identifies the technology stack behind any website.
Why it replaces Rex — API Client: Another popular Developer Tools extension: Identifies the technology stack behind any website.
5. Take Webpage Screenshots Entirely - FireShot
Take FULL webpage screenshots. Capture, edit and save them to PDF/JPEG/GIF/PNG, upload, print, send to OneNote, clipboard or email.
Why it replaces Rex — API Client: Another popular Developer Tools extension: Take FULL webpage screenshots. Capture, edit and save them to PDF/JPEG/GIF/PNG, upload, print, send to OneNote, clipboard or email.
6. Meta Ads Data Advisor
Meta Ads Data Advisor automates connecting your website and marketing data to Meta for better ad performance. No developers needed.
Why it replaces Rex — API Client: Another popular Developer Tools extension: Meta Ads Data Advisor automates connecting your website and marketing data to Meta for better ad performance. No developers needed.
7. Cookie-Editor
Simple yet powerful Cookie Editor that allow you to quickly create, edit and delete cookies without leaving your tab.
Why it replaces Rex — API Client: Another popular Developer Tools extension: Simple yet powerful Cookie Editor that allow you to quickly create, edit and delete cookies without leaving your tab.
8. Chromebook Recovery Utility
Create recovery media for your Chromebook.
Why it replaces Rex — API Client: Another popular Developer Tools extension: Create recovery media for your Chromebook.
9. Web Developer
Adds a toolbar button with various web developer tools.
Why it replaces Rex — API Client: Another popular Developer Tools extension: Adds a toolbar button with various web developer tools.
10. Lighthouse
Lighthouse is an open-source, automated tool for improving the performance, quality, and correctness of your web apps.
Why it replaces Rex — API Client: Another popular Developer Tools extension: Lighthouse is an open-source, automated tool for improving the performance, quality, and correctness of your web apps.
Compare Rex — API Client head-to-head
Direct comparisons with the extensions people weigh against it.
Wappalyzer vs JSON FormatterStack detection for recon work against readable API responses in the browser.React Developer Tools vs WappalyzerBoth are developer tools extensions people shortlist together — see how ratings, install base, pricing and day-to-day use differ.React Developer Tools vs JSON FormatterBoth are developer tools extensions people shortlist together — see how ratings, install base, pricing and day-to-day use differ.All comparisonsThe full compare hub, grouped by category.
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Frequently asked questions
What is the best alternative to Rex — API Client?
JSON Formatter is the closest match. Covers similar ground in the Developer Tools category: Makes raw JSON responses readable in the browser.
Is there a free alternative to Rex — API Client?
Yes — JSON Formatter, React Developer Tools, Tag Assistant are free.