The Referer header (note the historical misspelling) indicates the URL of the resource from which the current request originated. It helps servers understand navigation flows and traffic sources.

Browsers control whether to send this header based on the Referrer-Policy header set on the referring page. It is omitted for direct navigation, bookmarks, and when downgrading from HTTPS to HTTP.

Check if your website sends this header correctly

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Security Headers: CSP, HSTS, X-Frame-Options and More

How to protect your website with HTTP security headers. Configuring Content-Security-Policy, Strict-Transport-Security, X-Frame-Options, and other headers.

HTTP Headers: The Complete Guide

What are HTTP headers, their types, and how request and response headers work. Practical examples and recommendations for web developers.