API Tester
Make HTTP requests, test REST endpoints, and view responses with this lightweight API testing tool.
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About API Tester
Make HTTP requests, test REST endpoints, and view responses with this lightweight API testing tool. This tool is part of DevKit's collection of 32 free developer tools, all running entirely in your browser.
Whether you're debugging code, converting formats, or validating data, API Tester gives you instant results without any setup. No installations, no signups, no server round-trips — just open and use.
Free Forever
No cost, no hidden fees, no premium tiers.
Private by Design
Your data never leaves your browser.
Zero Latency
Results are instant — no server processing.
Key Features
Everything you need, nothing you don't.
100% Client-Side
All processing happens in your browser. No data is ever sent to a server.
Instant Results
No waiting for server responses. Get your results immediately as you type.
No Signup Needed
Just open and use. No accounts, no email, no tracking.
Dark Mode
Easy on the eyes. Toggle to light mode anytime, your preference is saved.
Works Everywhere
Compatible with all modern browsers including Chrome, Firefox, Safari, and Edge.
Copy & Go
One-click copy to clipboard. Get your results and get back to work instantly.
How to Use
Three simple steps. No friction.
Enter Your Input
Paste or type your data into the API Tester input field above. Everything stays in your browser.
Process Instantly
Results appear immediately as you interact. No loading screens, no waiting, no server round-trips.
Copy & Use
Copy the output with a single click and paste it wherever you need it. Done in seconds.
Common Use Cases
When and why developers reach for API Tester.
Development
Speed up your daily development workflow with API Tester. No context switching required.
Debugging
Quickly validate, format, and transform data while debugging your applications.
Learning
Experiment and learn how different formats and encodings work in real time.
Productivity
Skip the command line. Get the same results faster with a clean, intuitive interface.
Frequently Asked Questions
Everything you need to know about API Tester.
Yes, API Tester is completely free with no signup required. All tools on DevKit are 100% free and supported by display ads.
Absolutely. API Tester runs entirely in your browser using client-side JavaScript. Your data is never uploaded to any server — nothing leaves your device.
No installation required. API Tester works directly in your browser. Just open the page and start using it immediately.
Once the page is loaded, API Tester works offline since all processing happens client-side. You can bookmark it for quick access.
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