24890 2014-03-02 07:44:38 +0000 "89 [...] A byte with only the highest bit set" 2014-09-20 22:05:21 +0000 1 1 1 Unclassified WHATWG MIME unspecified All All RESOLVED FIXED P2 normal Unsorted 1 naesten gphemsley mike sideshowbarker+mimespec oldest_to_newest 101718 0 naesten 2014-03-02 07:44:38 +0000 http://mimesniff.spec.whatwg.org/#matching-an-image-type-pattern [[ 89 50 4E 47 0D 0A 1A 0A FF FF FF FF FF FF FF FF None. image/png A byte with only the highest bit set followed by the string "PNG" followed by CR LF SUB LF, the PNG signature. ]] 0x89 is *not* a byte with only the highest bit set. Looking at a random PNG file, it seems that it's the prose that's wrong here. <http://www.libpng.org/pub/png/spec/1.2/PNG-Rationale.html#R.PNG-file-signature> may be of interest here. 101724 1 gphemsley 2014-03-02 17:20:02 +0000 Interesting; you are correct. I definitely borrowed that description from somewhere, but I guess not the PNG spec itself. (I was thinking Wikipedia, but the current version of the article doesn't exactly match what I wrote here; perhaps its original description was different and has been changed.) 111890 2 gphemsley 2014-09-20 22:05:21 +0000 Fixed this by just referring to it as an "error-checking byte": https://github.com/whatwg/mimesniff/commit/6757c672535a77cf86cbfc3b3dbafb6657d4e4ac