php - Detect if browser supports WebP format? (server side) -

there thread detecting webp support using client-side. how detect webp support using server side?

today, should check accept header image/webp. browsers support webp send part of accept string requests (images , non-images). in short:

if( strpos( $_server['http_accept'], 'image/webp' ) !== false ) {     // webp supported! } 

(you might want use preg_match instead , add word boundary checks , case insensitivity, in real world should fine)

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here's original answer several years ago, when above not reliable

the "proper" way check accept header sent, bug in chrome means won't list image/webp though support it.

this relevant forum thread: https://groups.google.com/a/webmproject.org/forum/#!topic/webp-discuss/6nyupcsaors

which links bugtracker: https://code.google.com/p/chromium/issues/detail?id=169182 in turn links one: https://code.google.com/p/chromium/issues/detail?id=267212

end result? while isn't implemented yet, google chrome explicitly list image/webp accepted type both image and non-image requests. script serves html can check that. opera sends image/webp part of standard accept header (again regardless of whether image request or not).

so, check so:

if( strpos( $_server['http_accept'], 'image/webp' ) !== false || strpos( $_server['http_user_agent'], ' chrome/' ) !== false ) {     // webp supported! } 

(you might want use preg_match instead , add word boundary checks , case insensitivity, in real world should fine. might want check @ least version 6 of chrome, there's pretty nobody running out-of-date version there's not lot of point)