Developer Tools guides

Why "blocked by CORS policy" shows up in your console, what’s actually enforcing it, and the real ways to fix it depending on whether you control the API.

How to send a JSON POST request — the Content-Type header, the request body, and a live example you can open and test in the API Request Builder.

How to test API authentication — Bearer tokens, API keys, and Basic Auth — with live request examples you can open and send in the browser.

How to send multipart/form-data to an API — text form fields, file uploads, and the Content-Type mistake that breaks them — with live examples you can test.

Import a cURL command, inspect and test the request, then generate the equivalent JavaScript Fetch, Axios, Node.js, or Python Requests code.

DBML syntax explained — tables, columns, column settings, and Ref relationships — with a practical walkthrough of writing a schema that renders as a diagram.

Open a .postman_collection.json file without installing Postman — import a Collection v2.0/v2.1 in the browser and inspect, edit, and test its requests.

Test an OpenAPI 3.0 or 3.1 spec online — import the JSON or YAML file in the browser and turn its endpoints into editable, sendable API requests.

A reference for common API testing errors — what 400, 401, 403, 404, 405, 415, 422, 429 and 5xx status codes mean, plus timeouts and CORS failures, and what to check next.