---
title: New free tool: API Tester
description: Testing an API from the browser runs into CORS walls, and testing it from your laptop says nothing about how it looks from outside. The free API Tester sends…
canonical: https://watchfor.io/changelog/2026-08-09-free-api-tester
---

[All updates](/changelog/page/7#2026-08-09-free-api-tester) ✨ New Aug 9, 2026 · v 5.4.3

# New free tool: API Tester

Testing an API from the browser runs into CORS walls, and testing it from your laptop says nothing about how it looks from outside. The free API Tester sends a real HTTP request from one of our monitoring probes and shows the response — status, timing, headers and every JSON field flattened into a clickable list. GET, HEAD and POST are free with no signup. When you want it watched on a schedule, with assertions, extracted-value charts and alerts, one click turns it into an API monitor.

A real request from a probe, with every JSON field listed.

## What it does

Paste a URL, pick the method, add headers or a body if you need them, and send. The request goes out from one of our monitoring probes on the public internet, not from your browser, so there's no CORS error and no "works on my machine". You get back:

- the status code, the total time and the response size;

- every response header;

- the JSON body flattened into a list of fields, such as data.items.0.id = 42 , so you can read a large response at a glance.

## An example

Your mobile app reports errors from one endpoint, but it works from your laptop on the office network. You paste the endpoint into the API Tester and see it from outside: a 403 with a firewall's challenge page instead of JSON. That's your answer in ten seconds.

## When you want it watched

Start free under the result carries the URL over to your first monitor. Make it an [API monitor](/api-monitoring) and the same request runs on a schedule, with assertions on the fields, charts of the numbers you pick and an alert when it breaks.

Try it at [/api-tester](/api-tester). It's free with no signup, and requests are rate-limited to keep it fair.

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Canonical page: https://watchfor.io/changelog/2026-08-09-free-api-tester · Site guide: https://watchfor.io/llms.txt