By early 1992 the search was on for a good byte-stream encoding of multi-byte character sets. The draft ISO 10646 standard contained a non-required annex called UTF-1 that provided a byte-stream encoding of its 32-bit code points. This encoding was not satisfactory on performance grounds, but did introduce the notion that bytes in the range of 0–127 continue representing the ASCII characters in UTF, thereby providing backward compatibility with ASCII.
In July 1992, the X/Open committee XoJIG was looking for a better encoding. Dave Prosser of Unix System Laboratories submitted a proposal for one that had faster implementation characteristics and introduced the improvement that 7-bit ASCII characters would only represent themselves; all multibyte sequences would include only bytes where the high bit was set. This original proposal, FSS-UTF (File System Safe UCS Transformation Format), was similar in concept to UTF-8, but lacked the crucial property of self-synchronization.[7][8]
In August 1992, this proposal was circulated by an IBM X/Open representative to interested parties. Ken Thompson of the Plan 9 operating system group at Bell Labs then made a small but crucial modification to the encoding, making it very slightly less bit-efficient than the previous proposal but allowing it to be self-synchronizing, meaning that it was no longer necessary to read from the beginning of the string to find code point boundaries. Thompson's design was outlined on September 2, 1992, on a placemat in a New Jersey diner with Rob Pike. In the following days, Pike and Thompson implemented it and updated Plan 9 to use it throughout, and then communicated their success back to X/Open.[7]
UTF-8 was first officially presented at the USENIX conference in San Diego, from January 25 to 29, 1993.
Google reported that in 2008 UTF-8 (misleadingly labelled "Unicode") became the most common encoding for HTML files.[9][10]