cURL Builder
Build cURL commands visually without memorizing syntax. Set method, URL, headers, body, and authentication options, then copy the generated command.
Key features
- Support for all HTTP methods
- Visual header and body builder
- Bearer and Basic authentication
- Copy-ready cURL output
Guide
cURL (Client URL) is a command-line tool for transferring data using network protocols. It supports HTTP, HTTPS, FTP, and dozens of other protocols, but its primary use in modern development is making HTTP requests to APIs. Every web developer, backend engineer, and DevOps professional uses cURL regularly for testing endpoints, debugging API issues, and automating data transfers. This guide covers HTTP request construction, authentication methods, header management, data formatting, and practical patterns for API testing. A basic cURL command has the form: curl https://api.example.com/users. This sends a GET request to the specified URL and prints the response body to the terminal. By default, cURL uses GET, follows no redirects, sends no request body, and shows only the response body (not headers). Every other option builds on this foundation by modifying the method, adding headers, including a body, changing redirect behavior, or adjusting output format. Understanding this default behavior is essential because many debugging sessions start with figuring out which default you need to override. The -X flag (or --request) sets the HTTP method. curl -X POST https://api.example.com/users sends a POST request. curl -X PUT sends PUT. curl -X DELETE sends DELETE. curl -X PATCH sends PATCH. For GET requests, -X GET is optional because GET is the default. For HEAD requests, use -I (or --head) instead of -X HEAD, as -I also tells cURL to display the response headers. Some developers always include -X for clarity even with GET, which is fine. Using the long form (--request POST) makes scripts more readable. Request headers are set with the -H flag (or --header). Each header gets its own -H flag. curl -H "Content-Type: application/json" -H "Accept: application/json" sends two headers. Headers that cURL sets by default include Host (derived from the URL), User-Agent (curl/version), and Accept (*/*). Setting a header with -H overrides the default if the header name matches. To remove a default header, set it to an empty value: -H "User-Agent:" sends a request with no User-Agent header. This is useful for testing how servers handle missing headers. Sending JSON data is the most common POST/PUT/PATCH pattern. Use -d (or --data) for the request body and -H to set the content type: curl -X POST -H "Content-Type: application/json" -d '{"name":"John\
Frequently asked questions
What is cURL?
cURL is a command-line tool for transferring data using various protocols. It is commonly used for API testing and debugging.
Can I test APIs with this tool?
This tool generates the cURL command which you can paste into your terminal to test APIs directly.
