Google Chrome will begin to limit the HTTP Referer header to 4KiB in order to prevent attacks such as cache probing. Microsoft Edge and Mozilla Firefox have indicated that they will adopt this change as well. In a Google Chrome test conducted by Mike West, this change caused errors in 1 in 10,000 requests. Other browsers such as Mozilla Firefox and Microsoft Edge indicated they are on board with this change. When a browser sends a very long Referer to the header, the browser will return an HTTP error code.
Source: https://www.bleepingcomputer.com/news/security/google-chrome-to-limit-referer-header-size-to-block-attacks/