Specify a Character Set Early

HTML5 requires browsers to buffer a response when a character set is not specified in the Content-Type header or an HTML <meta> tag. Thus, we recommend always specifying a character set for HTMl documents.

Details

We tested character set buffering behavior with the following popular browsers:

• Internet Explorer: All versions of IE tested did not buffer responses. In contrast, all the other browsers tested do buffer when a character set is not specified. Note that when a character set is specified late in the document, Internet Explorer will redraw the page using the specified character set if it is not the same as the default character set.
• Firefox: Through version 3.5, specifying the Content-Type header as text/html, without specifying a character set, disables buffering in Firefox. Without a Content-Type header, Firefox buffers up to 1024 bytes. Firefox 3.6 buffers 512 bytes.
• Chrome: Chrome buffers up to 1024 bytes when a character set is not specified. Chrome will parse a character set from either the Content-Type HTTP header or the HTML META tag.
• Safari: Safari always buffers 1024 bytes, regardless of the contents of the Content-Type header or html META tag.

See also

• Zoompf also reports on this issue: Browser Performance Issues with Charsets.
• http://tools.ietf.org/html/draft-abarth-mime-sniff-01
• http://dev.w3.org/html5/spec/Overview.html#content-type-sniffing

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