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THE COLLECTION / 14 FREE TOOLS

HTTP & API tools

Test API requests, convert cURL commands, sanitize HAR files, validate OpenAPI specs and inspect HTTP headers. Each tool explains whether your input stays on your device or is sent to the address you choose.

Choose an HTTP or API tool

Reference

Plain-English explanations of HTTP status codes, with fixes for common errors.

HTTP Status Codes

Explains every common HTTP status code in plain language, with what to do about errors.

cURL converters

Turn cURL commands into fetch, axios or Python requests code.

cURL to Python

Converts cURL commands into Python code using the requests library.

cURL to fetch

Converts cURL commands into JavaScript fetch code, including headers, JSON bodies, forms and auth.

cURL to axios

Converts cURL commands into Node.js code using axios.

Inspect requests

Break down URLs, headers, cookies, user agents and Basic auth credentials, and read or clean HAR recordings.

CSP Analyzer

Reviews a Content Security Policy directive by directive, explains what actually applies after fallbacks, and builds a new policy for your server.

HAR Analyzer

Opens a HAR file to show every request, its timing and errors, and makes a cleaned copy with cookies, tokens and passwords removed before you share it.

URL Parser

Breaks a URL into its parts and decodes every query parameter, flagging tracking parameters.

User Agent Parser

Identifies the browser, rendering engine, operating system and device type from a user agent string.

Headers Analyzer

Explains HTTP response headers and checks for missing security headers and version leaks.

Cookie Parser

Parses Cookie and Set-Cookie headers, explains every attribute and flags insecure or broken cookies.

Basic Auth Header

Creates an HTTP Basic Authorization header from a username and password, and decodes existing ones.

API testing & specs

Send requests and export reports, or validate OpenAPI and Swagger documents and browse their endpoints.

Request Tester

Sends an HTTP request from your browser — built by hand or pasted as cURL — and writes the request and response up as Markdown or plain text, with tokens and passwords hidden.

OpenAPI Validator

Checks an OpenAPI or Swagger document for the mistakes that break code generators and gateways, and shows its endpoints in a readable list.

IP & networking

Work out subnets, masks and address ranges, for IPv4 and IPv6.

Subnet Calculator

Works out the network address, usable range, mask and host count for any IPv4 or IPv6 block, and splits it into smaller subnets.

About HTTP & API tools

Inspect an API from its definition through to a real response: validate OpenAPI or Swagger documents, convert cURL into JavaScript or Python, send requests, and export a request and response as Markdown. For browser debugging, examine HAR timings, sanitize recordings, check security headers and Content Security Policy, or look up an HTTP status code.

Parsers, validators and converters process your input locally. The HTTP Request Tester is the exception: it sends a request directly from your browser to the address you enter, with no proxy or saved history. The destination must allow browser access through CORS; exporting a request as Markdown does not require sending it.

Frequently asked questions

Can I send an HTTP request from this site?

Yes. The HTTP Request Tester sends requests directly from your browser to the URL you enter. It has no proxy, so the destination must permit browser access through CORS. Other tools analyze pasted text or files locally.

Which tool should I use for a HAR file?

The HAR Analyzer & Sanitizer displays requests and timings and removes common credentials from an exported copy. Review the result before sharing: custom application data may still contain private information.

Does checking headers or an API spec contact the server?

No. The HTTP Headers Analyzer, CSP Analyzer and OpenAPI Validator inspect the content you paste or open. Only the HTTP Request Tester sends a request when you choose Send.