In the "Accept-Encoding" header of an HTTP request, you'll typically find gzip, deflate, indicating the client's supported encoding types.

gzip: A popular compression algorithm that effectively reduces data size during transmission. When the server includes "gzip" in the response header, it indicates support for compressing response data using the gzip algorithm. Most modern browsers support gzip compression.

deflate: Another compression algorithm used to reduce data size during transmission. When the server includes "deflate" in the response header, it indicates support for compressing response data using the deflate algorithm. Most modern browsers also support deflate compression.

br: Brotli is a next-generation compression algorithm that typically provides better compression rates than gzip and deflate, thereby reducing data size during transmission. When the server includes "br" in the response header, it indicates support for compressing response data using the Brotli algorithm. However, support for Brotli compression is relatively new in browsers, so it may not be supported on some older browsers.

When a client browser sends a request, it lists the compression algorithms it supports in the "Accept-Encoding" header. Based on these algorithms, the server selects the most appropriate compression method to reduce bandwidth consumption and improve performance during data transmission. Typically, servers prioritize Brotli (br) first, followed by gzip, and then deflate to provide optimal compression. If the client browser doesn't support any of these compression algorithms, the server transmits content uncompressed, which helps enhance the user experience on the website.