API Tester
Featured
Send HTTP requests from your browser and inspect responses.
- On your device
- No signup
Developer topic guide
API debugging tools
Test APIs, format responses, build cURL, and inspect JWTs—free API debugging on your device.
5 free tools in this guide — pick one below to get started.
Tools in this guide(5)
Open a tool to calculate, convert, or edit — no signup required.
API Response Formatter
Featured
Pretty-print JSON or XML API responses with auto-detection.
- On your device
- No signup
cURL Builder
Featured
Build curl commands from method, URL, headers, and body.
- On your device
- No signup
JSON Compare
Featured
Compare two JSON documents and list structural differences.
- On your device
- No signup
JWT Decoder
Featured
Decode JWT header, payload, and expiry—including Bearer tokens—on your device.
- On your device
- No signup
Overview
API debugging tools reproduce requests, pretty-print responses, and inspect tokens during integration work. This topic guide groups Utilnivo tools so you can move from rough estimates to a concrete next step without hunting across categories.
Start with the tool that matches your immediate question—api tester, api response formatter, curl builder, json compare, jwt decoder—then open related tools, workflows, or long-tail pages when you need comparisons, exports, or follow-up checks.
Outputs are educational. Confirm numbers with professionals, instructors, or platform requirements before you sign, submit, or publish.
How to choose
- Api Tester → api-tester.
- Api Response Formatter → api-response-formatter.
- Curl Builder → curl-builder.
- Json Compare → json-compare.
- Jwt Decoder → jwt-decoder.
Frequently asked questions
Who is API debugging tools for?
Backend and full-stack developers tracing failing endpoints. Start with api tester, api response formatter, curl builder, then open related topic guides when your task spans multiple steps.
Which tool should I use first in API debugging tools?
Use the how-to-choose list on this page—it maps common tasks to specific tools. API debugging tools reproduce requests, pretty-print responses, and inspect tokens during integration work.
Are these tools free?
Yes. Utilnivo tools are free for standard browser use with no account required.
Is my data stored online?
Calculations and file processing for standard tools run on your device unless a page explicitly performs a network lookup.
Step-by-step workflows (3)
Multi-step guides that chain tools from this topic—follow numbered steps instead of guessing tool order.
- Debug a failing APIReproduce the request, format the JSON response, inspect JWTs, and compare payloads.5 steps
- Debug a JWT or API tokenDecode a bearer token, pretty-print JSON claims, and inspect Base64 segments.3 steps
- Validate JSON before deployValidate syntax, pretty-print, generate a schema draft, and diff against the previous payload.4 steps