Pre-installed on most Linux distros and macOS. Install on Ubuntu/Debian:

sudo apt install curl -y

Help: curl -h or curl —help all or man curl

Send a GET request and print response to STDOUT

curl <URL>

Verbose; shows full request and response headers

curl -v <URL>

More verbose detail

curl -vvv <URL>

Flag	Description	Example
-v	Verbose — show request and response headers	curl -v http://example.com↗
-I	Send HEAD request — show response headers only	curl -I http://example.com↗
-i	Include response headers in output (full response)	curl -i http://example.com↗
-H	Set a custom request header	curl -H ‘Content-Type: application/json’ <URL>
-A	Set User-Agent string	curl -A ‘Mozilla/5.0’ <URL>
-X	Specify HTTP method	curl -X POST <URL>
-d	Send POST body data	curl -d ‘username=admin&password=admin’ <URL>
-u	Pass username:password for basic auth	curl -u admin:password <URL>
-b	Send a cookie with the request	curl -b ‘PHPSESSID=abc123’ <URL>
-L	Follow redirects	curl -L <URL>
-O	Save output to file using remote filename	curl -O http://example.com/file.zip↗
-o	Save output to a specified file	curl -o myfile.zip <URL>
-s	Silent mode — suppress progress output	curl -s <URL>
-k	Skip SSL certificate verification	curl -k https://local-dev.example.com↗

Raw HTML to STDOUT

curl http://example.com

Full request/response with headers

curl -v http://example.com

Headers only (HEAD request)

curl -I http://example.com

curl -X POST -d 'username=admin&password=admin' http://<IP>:<PORT>/login.php

Add -L to follow the redirect that most login forms issue after successful auth:

curl -X POST -d 'username=admin&password=admin' -L http://<IP>:<PORT>/login.php

Use -b to include a session cookie obtained after login:

curl -b 'PHPSESSID=c1nsa6op7vtk7kdis7bcnbadf1' http://<IP>:<PORT>/dashboard

POST with cookie and JSON body:

curl -X POST -d '{"search":"london"}' -b 'PHPSESSID=c1nsa6op7vtk7kdis7bcnbadf1' -H 'Content-Type: application/json' http://<IP>:<PORT>/search.php

Using -u flag:

curl -u admin:password http://<IP>:<PORT>/admin

Alternatively embed credentials in URL:

curl http://admin:password@<IP>:<PORT>/admin

Manually set Authorization header with base64 encoded credentials:

curl -H 'Authorization: Basic YWRtaW46cGFzc3dvcmQ=' http://<IP>:<PORT>/admin

Set custom headers:

curl -H 'X-Forwarded-For: 127.0.0.1' http://example.com

Skip SSL verification (for self-signed or expired certs):

curl -k https://example.com

Read (GET):

curl http://<IP>:<PORT>/api.php/city/london

Pipe to jq for formatted JSON output: curl http://<IP>:<PORT>/api.php/city/ | jq

Create (POST):

curl -X POST http://<IP>:<PORT>/api.php/city/ -d '{"city_name":"HTB_City","country_name":"HTB"}' -H 'Content-Type: application/json'

Update (PUT):

curl -X PUT http://<IP>:<PORT>/api.php/city/london -d '{"city_name":"New_City","country_name":"HTB"}' -H 'Content-Type: application/json'

Delete (DELETE):

curl -X DELETE http://<IP>:<PORT>/api.php/city/New_City

Use -X OPTIONS to check which methods the API accepts.

1. Open DevTools (F12 or Ctrl+Shift+I) → Network tab
2. Perform the action in the browser
3. Right-click the request → Copy → Copy as cURL
4. Paste the full curl command into terminal — all headers and cookies included

Connect to IMAP over TLS and enumerate banner/certificate:

curl -k 'imaps://<target>' --user <user>:<pass>

curl -k 'imaps://<target>' --user <user>:<pass> -v

— Verbose output reveals TLS version, full SSL certificate (CN, org, expiry), and server banner including mail server version

POP3 over TLS:

curl -k 'pop3s://<target>' --user <user>:<pass> -v