Content negotiation: List of default Accept values

List of default Accept values

This article documents the default values for the HTTP Accept header for specific inputs and browser versions.

Default values

These are the values sent when the context doesn't give better information. Note that all browsers add the */* MIME Type to cover all cases. This is typically used for requests initiated via the address bar of a browser, or via an HTML <a> element.

User Agent	Value
Firefox 92 and later [1]	`text/html,application/xhtml+xml,application/xml;q=0.9,image/avif,image/webp,/;q=0.8`
Firefox 72 to 91 [1]	`text/html,application/xhtml+xml,application/xml;q=0.9,image/webp,/;q=0.8`
Firefox 66 to 71 [1]	`text/html,application/xhtml+xml,application/xml;q=0.9,/;q=0.8`
Firefox 65 [1]	`text/html,application/xhtml+xml,application/xml;q=0.9,image/webp,/;q=0.8`
Firefox 64 and earlier [1]	`text/html,application/xhtml+xml,application/xml;q=0.9,/;q=0.8`
Safari, Chrome	`text/html,application/xhtml+xml,application/xml;q=0.9,image/webp,image/apng,/;q=0.8`
Safari 5 [2]	`text/html,application/xhtml+xml,application/xml;q=0.9,/;q=0.8`
Internet Explorer 8 [3]	`image/jpeg, application/x-ms-application, image/gif, application/xaml+xml, image/pjpeg, application/x-ms-xbap, application/x-shockwave-flash, application/msword, /`
Edge	`text/html, application/xhtml+xml, image/jxr, /`
Opera	`text/html, application/xml;q=0.9, application/xhtml+xml, image/png, image/webp, image/jpeg, image/gif, image/x-xbitmap, /;q=0.1`

[1] This value can be modified using the network.http.accept.default parameter.

[2] This is an improvement over earlier Accept headers as it no longer ranks image/png above text/html.

[3] See IE and the Accept Header (IEInternals' MSDN blog).

Values for an image

When requesting an image, like through an HTML <img> element, user-agent often sets a specific list of media types to be welcomed.

User Agent	Value
Firefox 92 and later [1]	`image/avif,image/webp,/`
Firefox 65 to 91 [1]	`image/webp,/`
Firefox 47 to 63 [1]	`/`
Firefox prior to 47 [1]	`image/png,image/;q=0.8,/*;q=0.5`
Safari (since Mac OS Big Sur)	`image/webp,image/png,image/svg+xml,image/;q=0.8,video/;q=0.8,/;q=0.5`
Safari (before Mac OS Big Sur)	`image/png,image/svg+xml,image/;q=0.8,video/;q=0.8,/;q=0.5`
Chrome	`image/avif,image/webp,image/apng,image/,/*;q=0.8`
Internet Explorer 9	`image/png,image/svg+xml,image/;q=0.8, /*;q=0.5`
Internet Explorer 8 or earlier source	`/`

[1] This value can be modified using the image.http.accept parameter (source).

Values for a video

When a video is requested, via the <video> HTML element, most browsers use specific values.

User Agent	Value
Firefox 3.6 and later	`video/webm,video/ogg,video/;q=0.9,application/ogg;q=0.7,audio/;q=0.6,/;q=0.5`
Firefox earlier than 3.6	no support for `<video>`
Chrome	`/`
Internet Explorer 8 or earlier	no support for `<video>`

Values for audio resources

When an audio file is requested, like via the <audio> HTML element, most browsers use specific values.

User Agent	Value
Firefox 3.6 and later [1]	`audio/webm,audio/ogg,audio/wav,audio/;q=0.9,application/ogg;q=0.7,video/;q=0.6,/;q=0.5`
Safari, Chrome	`/`
Internet Explorer 8 or earlier	no support for `<audio>`
Internet Explorer 9	?

[1] See bug 489071.

Values for scripts

When a script is requested, like via the <script> HTML element, some browsers use specific values.

User Agent	Value
Firefox [1]	`/`
Safari, Chrome	`/`
Internet Explorer 8 or earlier [2]	`/`
Internet Explorer 9	`application/javascript, /;q=0.8`

[1] See bug 170789.

[2] See IE and the Accept Header (IEInternals' MSDN blog).

Values for a CSS stylesheet

When a CSS stylesheet is requested, via the <link rel="stylesheet"> HTML element, most browsers use specific values.

User Agent	Value
Firefox 4 [1]	`text/css,/;q=0.1`
Internet Explorer 8 or earlier [2]	`/`
Internet Explorer 9	`text/css`
Safari, Chrome	`text/css,/;q=0.1`
Opera 11.10	`text/html, application/xml;q=0.9, application/xhtml+xml, image/png, image/webp, image/jpeg, image/gif, image/x-xbitmap, /;q=0.1`
Konqueror 4.6	`text/css,/;q=0.1`