API, HTTP & Network Tools
Test your internet speed, look up status codes and headers, parse URLs, send requests and turn cURL into fetch, Axios or Python.
21 tools · most run in your browser; the rest say what they send
Popular
Subnet Calculator
IPv4 & IPv6 CIDR subnet calculator with binary bit breakdown.
MAC Address Lookup
Identify hardware vendors, normalize MAC formats, and decode OUI bits.
cURL to Fetch Converter
Convert a curl command to JavaScript fetch code.
HTTP Status Code Lookup
Look up any HTTP status code: meaning, causes and how to fix it.
URL Parser
Break a URL into scheme, host, port, path, query and fragment.
HTTP Header Analyzer
Paste HTTP headers to see what each means and what to fix.
All API, HTTP & Network tools
Content-Type Header Checker
Pick, check or detect the right Content-Type header.
cURL Command Generator
Build a correct curl command from a form, for any shell.
cURL to Axios Converter
Convert a curl command to Axios code for JavaScript.
cURL to Fetch Converter
Convert a curl command to JavaScript fetch code.
cURL to JavaScript Converter
Convert curl to fetch, XMLHttpRequest, Node.js https or jQuery.
cURL to Python Converter
Convert a curl command to Python requests, httpx or urllib.
HTTP Header Analyzer
Paste HTTP headers to see what each means and what to fix.
HTTP Header Generator
Generate security, CORS, cache and CSP headers for your server.
HTTP Method Reference
GET, POST, PUT, PATCH, DELETE: safe, idempotent, cacheable.
HTTP Status Code Lookup
Look up any HTTP status code: meaning, causes and how to fix it.
IPv4 to IPv6 Converter
Convert IPv4 to mapped, 6to4, hex, and compress or expand IPv6.
MAC Address Lookup
Identify hardware vendors, normalize MAC formats, and decode OUI bits.
MIME Type Lookup
Find the MIME type for any file extension, and back.
Query String Builder
Build a correctly encoded query string from rows or JSON.
Query String Parser
Turn a query string into a table or JSON, decoded.
SSL Certificate Decoder
Inspect X.509 certificates and CSRs, validity dates, SANs, and keys.
Subnet Calculator
IPv4 & IPv6 CIDR subnet calculator with binary bit breakdown.
URL Parser
Break a URL into scheme, host, port, path, query and fragment.
User-Agent Parser
Identify the browser, OS, device or bot behind a User-Agent.
About these tools
Working with web APIs means constantly reading and writing the small details of HTTP: which status code means what, what a header does, how a query string is encoded, how a curl example from the documentation becomes code in your own language. These tools cover those jobs directly. Look up any status code or method, paste headers to have them explained and checked, break a URL into its parts, build a query string or a full request, and convert a curl command to fetch, Axios or Python.
Everything that can run in your browser does. Headers, URLs, user agents and curl commands are parsed on your device and never uploaded. Two tools use the network on purpose, and say so on their page: the API Request Builder sends the request you build directly from your browser to the address you enter, and the Internet Speed Test exchanges test data with Cloudflare's servers.
The converters read curl the way curl itself does, and their output was checked against a real curl on a local server, so the code you copy sends the same request the command would.
Guides
Step-by-step walkthroughs for jobs these tools handle.