# cURL — Transfer Data from the Command Line > Practical guide to cURL — HTTP requests, headers, authentication, downloads and TLS on the command line, with examples for every use case. Source: https://www.jpkc.com/db/en/cheatsheets/networking/curl/ cURL is the Swiss Army knife for HTTP on the command line: a single command lets you call APIs, download files, probe endpoints or debug headers. It speaks more than twenty protocols – from HTTP and HTTPS through FTP to SFTP – and ships on virtually every system. This guide walks you through the options you reach for daily, from a plain GET request to client-certificate authentication. ## Basic Requests `curl ` — Perform a simple GET request and print the response to stdout. ```bash curl https://api.example.com/users ``` `curl -s ` — Silent mode. Suppress progress meter and error messages. ```bash curl -s https://api.example.com/users ``` `curl -v ` — Verbose mode. Show request and response headers for debugging. ```bash curl -v https://api.example.com/users ``` `curl -I ` — Fetch only the HTTP response headers (HEAD request). ```bash curl -I https://www.example.com ``` `curl -L ` — Follow redirects automatically. ```bash curl -L https://example.com/redirect ``` ## Headers `curl -H "
" ` — Send a custom request header. ```bash curl -H "Accept: application/json" https://api.example.com/users ``` `curl -H "Content-Type: application/json" ` — Set the content type header for the request. ```bash curl -H "Content-Type: application/json" https://api.example.com/users ``` `curl -H "Authorization: Bearer " ` — Send a Bearer token for authentication. ```bash curl -H "Authorization: Bearer eyJhbGci..." https://api.example.com/me ``` `curl -A "" ` — Set a custom User-Agent string. ```bash curl -A "Mozilla/5.0" https://www.example.com ``` ## POST & PUT Data `curl -X POST -d "" ` — Send a POST request with URL-encoded form data. ```bash curl -X POST -d "name=John&email=john@example.com" https://api.example.com/users ``` `curl -X POST -H "Content-Type: application/json" -d '' ` — Send a POST request with JSON body. ```bash curl -X POST -H "Content-Type: application/json" -d '{"name":"John"}' https://api.example.com/users ``` `curl -X PUT -d '' ` — Send a PUT request to update a resource. ```bash curl -X PUT -H "Content-Type: application/json" -d '{"name":"Jane"}' https://api.example.com/users/1 ``` `curl -X PATCH -d '' ` — Send a PATCH request for partial updates. ```bash curl -X PATCH -H "Content-Type: application/json" -d '{"email":"new@example.com"}' https://api.example.com/users/1 ``` `curl -X DELETE ` — Send a DELETE request to remove a resource. ```bash curl -X DELETE https://api.example.com/users/1 ``` `curl -F "file=@" ` — Upload a file using multipart form data. ```bash curl -F "file=@photo.jpg" https://api.example.com/upload ``` `curl -d @ ` — Send data from a file as the request body. ```bash curl -d @data.json -H "Content-Type: application/json" https://api.example.com/users ``` ## Authentication `curl -u : ` — Send a request with Basic authentication. ```bash curl -u admin:secret https://api.example.com/admin ``` `curl -u ` — Prompt for password interactively (more secure). ```bash curl -u admin https://api.example.com/admin ``` `curl --oauth2-bearer ` — Send a request with an OAuth 2.0 Bearer token. ```bash curl --oauth2-bearer eyJhbGci... https://api.example.com/me ``` `curl -b "" ` — Send cookies with the request. ```bash curl -b "session=abc123" https://www.example.com/dashboard ``` `curl -c ` — Save response cookies to a file. ```bash curl -c cookies.txt https://www.example.com/login ``` ## Download & Output `curl -o ` — Save the response to a specific file. ```bash curl -o page.html https://www.example.com ``` `curl -O ` — Save the response using the remote filename. ```bash curl -O https://example.com/file.tar.gz ``` `curl -w "%{http_code}" -o /dev/null -s ` — Get only the HTTP status code. ```bash curl -w "%{http_code}" -o /dev/null -s https://www.example.com ``` `curl -w "%{time_total}" -o /dev/null -s ` — Measure the total response time. ```bash curl -w "%{time_total}" -o /dev/null -s https://www.example.com ``` `curl -C - -O ` — Resume an interrupted download. ```bash curl -C - -O https://example.com/largefile.zip ``` ## SSL/TLS `curl -k ` — Skip SSL certificate verification (insecure, for testing only). ```bash curl -k https://self-signed.example.com ``` `curl --cacert ` — Use a custom CA certificate for verification. ```bash curl --cacert ca-bundle.crt https://api.example.com ``` `curl --cert --key ` — Use client certificate authentication. ```bash curl --cert client.crt --key client.key https://api.example.com ``` ## Advanced Options `curl -x ` — Use a proxy server for the request. ```bash curl -x http://proxy.example.com:8080 https://www.example.com ``` `curl --connect-timeout ` — Set maximum time for the connection phase. ```bash curl --connect-timeout 5 https://api.example.com ``` `curl -m ` — Set maximum time for the entire operation. ```bash curl -m 30 https://api.example.com/slow-endpoint ``` `curl --retry ` — Retry the request on transient errors. ```bash curl --retry 3 https://api.example.com/flaky ``` `curl -s | jq .` — Pipe JSON response to jq for pretty-printing. ```bash curl -s https://api.example.com/users | jq . ``` ## Conclusion cURL belongs in every developer's and administrator's toolkit: what starts as a quick API test soon replaces whole scripts. If you regularly build complex requests, it pays to explore `--config` files and the `-w` output format for machine-readable results – turning a one-liner into a reusable tool. ## Further Reading - [curl – official documentation](https://curl.se/docs/) – reference and manual - [curl(1) – manual page](https://curl.se/docs/manpage.html) – every option at a glance - [cURL – Wikipedia](https://en.wikipedia.org/wiki/CURL) – background and history ## Related Commands - [httpie](https://www.jpkc.com/db/en/cheatsheets/networking/httpie/) – modern, user-friendly HTTP client - [wget](https://www.jpkc.com/db/en/cheatsheets/networking/wget/) – download files and entire sites - [dig](https://www.jpkc.com/db/en/cheatsheets/networking/dig/) – check DNS resolution before sending requests