Issue link: https://read.uberflip.com/i/1146286
94 | Chapter 13: Rule 13: Configure ETags In Apache, you can remove Etags by simply adding the following line to your Apache configuration file: FileETag none ETags in the Real World Table 13-1 shows that 6 out of 10 top U.S. web sites use ETags on a majority of their components. To be fair, three of them have modified the ETag format to remove inode (Apache) or ChangeNumber (IIS). Four or more contain ETags that haven't been modified and therefore cause the performance problems discussed previously. An example of a component with different ETags across the cluster of servers is http:// stc.msn.com/br/hp/en-us/css/15/blu.css from http://msn.com. The HTTP headers from the first request in the example contains an ETag value of 80b31d5a4776c71:6e0. GET /br/hp/en-us/css/15/blu.css HTTP/1.1 Host: stc.msn.com HTTP/1.1 200 OK Last-Modified: Tue, 03 Apr 2007 23:25:23 GMT ETag: "80b31d5a4776c71:6e0" Content-Length: 647 Server: Microsoft-IIS/6.0 On the first reload, the ETag matches and a 304 response is sent. The Content-Length header is missing from the response because the 304 status code tells the browser to use the content from its cache. GET /br/hp/en-us/css/15/blu.css HTTP/1.1 Host: stc.msn.com If-Modified-Since: Tue, 03 Apr 2007 23:25:23 GMT If-None-Match: "80b31d5a4776c71:6e0" Table 13-1. ETags observed across 10 top web sites Web Site Components with ETags Fixed http://www.amazon.com 0% (0/24) n/a http://www.aol.com 5% (3/63) yes http://www.cnn.com 83% (157/190) no http://www.ebay.com 86% (57/66) no http://www.google.com 0% (0/5) n/a http://www.msn.com 72% (42/58) no http://www.myspace.com 84% (32/38) yes and no http://www.wikipedia.org 94% (16/17) unknown http://www.yahoo.com 0% (0/34) n/a http://www.youtube.com 70% (43/61) yes