 | This article may be too technical for most readers to understand. (September 2024) |
 | This article includes a list of references, related reading, or external links, but its sources remain unclear because it lacks inline citations. (September 2024) |
| MIME / IANA | ISO-10646-UTF-1 |
|---|---|
| Language(s) | International |
| Current status | Obscure, of mainly historical interest. |
| Classification | Unicode Transformation Format, extended ASCII, variable-width encoding |
| Extends | US-ASCII |
| Transforms / Encodes | ISO/IEC 10646 (Unicode) |
| Succeeded by | UTF-8 |
UTF-1 is an obsolete method of transforming ISO/IEC 10646/Unicode into a stream of bytes. Its design does not provide self-synchronization, which makes searching for substrings and error recovery difficult. It reuses the ASCII printing characters for multi-byte encodings, making it unsuited for some uses (for instance Unix filenames cannot contain the byte value used for forward slash). UTF-1 is also slow to encode or decode due to its use of division and multiplication by a number which is not a power of 2. Due to these issues, it did not gain acceptance and was quickly replaced by UTF-8.