Show Curl Headers

The short answer

By default, the curl command will only write to the standard output (i.e. stdout) the message body of the response. If you want to also include the HTTP headers and the status code of the response in the output, you can use the -i flag (short for include) as follows:

 $ curl -i <url>

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Where:

• <url> is the URL of the target server (e.g. https://example.com, 127.0.0.1:3000).

Which will output something similar to this:

 HTTP/1.1 200 OK
 X-Powered-By: Express
 Content-Type: text/plain; charset=utf-8
 Content-Length: 2
 ETag: W/"2-nOO9QiTIwXgNtWtBJezz8kv3SLc"
 Date: Fri, 07 Apr 2023 09:14:17 GMT
 Connection: keep-alive
 Keep-Alive: timeout=5

 OK

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This flag is often used by developers to get detailed information about how the server processed their request. For example, when performing basic authentication or sending JSON data.

Easily retrieve this command using Warp’s AI Command Search

If you’re using Warp as your terminal, you can easily retrieve this command using the Warp AI Command Search feature:

Entering curl include response headers with message body in the AI Command Search will prompt curl -i, which can then quickly be inserted into your shell by doing CMD+ENTER.

Get the curl response headers only

To show the HTTP headers of the response only (i.e. without the message body), you can use the -I flag (capital “i”) as follows:

 $ curl -I <url>

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Which under the hood, will configure curl to send a HEAD request to the server indicating that only the headers of the requested resource should be returned but not its content.

For example:

 $ curl -I 127.0.0.1:3000
 HTTP/1.1 200 OK
 X-Powered-By: Express
 Content-Type: text/plain; charset=utf-8
 Content-Length: 2
 ETag: W/"2-nOO9QiTIwXgNtWtBJezz8kv3SLc"
 Date: Fri, 07 Apr 2023 11:02:10 GMT
 Connection: keep-alive
 Keep-Alive: timeout=5

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This flag is particularly useful when you want to retrieve the file size (i.e. the Content-Length header) and the last modification date (i.e. the Last-Modified header) of a resource located on a FTP server without actually downloading it.

Note that if you try to use this flag in conjunction with another HTTP method such as POST, curl might throw the following error:

 $ curl -I -X POST -H 
 ‘Content-Type: application/json’ -d ‘{“token”:”h3ll0”}’ https://example.com
 Warning: You can only select one HTTP request method! You asked for both POST
 Warning: (-d, --data) and HEAD (-I, --head).

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Get both the curl request and response headers

For debugging purposes, it is sometimes useful to see exactly what is going on under the hood when sending a request with `curl`.

To make curl output the HTTP headers of both the request and the response, including the message body of the response and additional information provided by `curl` itself, you can use the `-v` flag (short for verbose) as follows:

 $ curl -v <url>

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Where the output is delineated by:

• > representing the data sent.
• < representing the data received.
• * representing additional information.

For example:

 $ curl -v 127.0.0.1:3000
 *   Trying 127.0.0.1:3000...
 * Connected to 127.0.0.1 (127.0.0.1) port 3000 (#0)
 > GET / HTTP/1.1
 > Host: 127.0.0.1:3000
 > User-Agent: curl/7.85.0
 > Accept: */*
 >
 * Mark bundle as not supporting multiuse
 < HTTP/1.1 200 OK
 < X-Powered-By: Express
 < Content-Type: text/plain; charset=utf-8
 < Content-Length: 2
 < ETag: W/"2-nOO9QiTIwXgNtWtBJezz8kv3SLc"
 < Date: Fri, 07 Apr 2023 11:01:19 GMT
 < Connection: keep-alive
 < Keep-Alive: timeout=5
 <
 * Connection #0 to host 127.0.0.1 left intact

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