Hixie's Natural Log

2006-04-11 22:22 UTC Content-Type is dead

Browsers and other user agents largely ignore the HTTP Content-Type header, relying on undefined sniffing heuristics to determine what the content of a page really is.

Unfortunately, we're now at a stage where browsers are continuously having to reverse-engineer each other to determine why they are handling content differently. A browser can't afford to render any less content than a browser with more market share, because otherwise users won't switch, and the new browser will not be adopted.

I think it may be time to retire the Content-Type header, putting to sleep the myth that it is in any way authoritative, and instead have well-defined content-sniffing rules for Web content.

I have some tests that look at the state of MIME type sniffing, if you need convincing that the state of Content-Type on the Web is a lost cause.

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