How to Include Response Headers in Curl Output

When debugging web requests or testing APIs, you often need to view the HTTP response headers alongside the actual response body. This article explains how to instruct the curl command-line tool to include response headers in its standard output using the -i option, and covers alternative methods for viewing header metadata depending on your specific troubleshooting needs.

Use the -i (or --include) Option

To include the HTTP response headers in your normal output along with the response body, use the -i or --include option. This tells curl to print the protocol headers before the actual document content.

Run the following command in your terminal:

curl -i https://api.github.com

Understanding the Output

When you run this command, the output is split into two distinct parts:

1. The Headers: At the very top, you will see the HTTP status line (e.g., HTTP/2 200) followed by the response headers (such as Content-Type, Server, Date, etc.).
2. The Body: After the headers, there is a single blank line, followed immediately by the standard response payload (HTML, JSON, or plain text).

Alternative: Show Headers Only with -I (or --head)

If you only want to inspect the response headers and do not want to download or view the response body, use the uppercase -I or --head option. This performs a HEAD request instead of a GET request.

curl -I https://api.github.com

Note: Some servers handle HEAD requests differently than GET requests, but this is the fastest way to inspect headers without downloading large files.

Alternative: Verbose Mode with -v (or --verbose)

For deeper troubleshooting, the -v or --verbose option prints the entire communication process. This includes the SSL/TLS handshake, the request headers sent by your machine (prefixed with >), and the response headers received from the server (prefixed with <).

curl -v https://api.github.com

Unlike -i, which prints the response headers directly to standard output (stdout), verbose mode prints debugging information to standard error (stderr), keeping your saved output file clean if you redirect the response.