The next 1,920 code points need two bytes to encode, which covers the remainder of almost all Latin-script alphabets, and also IPA extensions, Greek, Cyrillic, Coptic, Armenian, Hebrew, Arabic, Syriac, Thaana and N'Ko alphabets, as well as Combining Diacritical Marks. The first 128 code points (ASCII) need one byte. In the following table, the x characters are replaced by the bits of the code point: UTF-8 encodes code points in one to four bytes, depending on the value of the code point. In HP PCL, UTF-8 is called Symbol-ID "18N". In MySQL, UTF-8 is called utf8mb4 ( utf8mb3, and its alias utf8, is there a subset encoding). In Windows, UTF-8 is codepage 65001 (i.e. In Japan especially, UTF-8 encoding without a BOM is sometimes called " UTF-8N". " UTF-8-BOM" and " UTF-8-NOBOM" are sometimes used for text files which contain or don't contain a byte order mark (BOM), respectively. Despite this, most web browsers can understand them, and so standards intended to describe existing practice (such as HTML5) may effectively require their recognition. " utf8" or " UTF 8", are not accepted as correct by the governing standards. Other variants, such as those that omit the hyphen or replace it with a space, i.e. However, the name " utf-8" may be used by all standards conforming to the IANA list (which include CSS, HTML, XML, and HTTP headers), as the declaration is case-insensitive. This spelling is used in all the Unicode Consortium documents relating to the encoding. All letters are upper-case, and the name is hyphenated. The official Internet Assigned Numbers Authority (IANA) code for the encoding is " UTF-8". Virtually all countries and languages have 95.0% or more use of UTF-8 encodings on the web. UTF-8 is the dominant encoding for the World Wide Web (and internet technologies), accounting for 97.9% of all web pages, over 99.0% of the top 10,000 pages, and up to 100.0% for many languages, as of 2023. This led to its adoption by X/Open as its specification for FSS-UTF, which would first be officially presented at USENIX in January 1993 and subsequently adopted by the Internet Engineering Task Force (IETF) in RFC 2277 ( BCP 18) for future internet standards work, replacing Single Byte Character Sets such as Latin-1 in older RFCs. Ken Thompson and Rob Pike produced the first implementation for the Plan 9 operating system in September 1992. UTF-8 was designed as a superior alternative to UTF-1, a proposed variable-length encoding with partial ASCII compatibility which lacked some features including self-synchronization and fully ASCII-compatible handling of characters such as slashes. It was designed for backward compatibility with ASCII: the first 128 characters of Unicode, which correspond one-to-one with ASCII, are encoded using a single byte with the same binary value as ASCII, so that valid ASCII text is valid UTF-8-encoded Unicode as well. Code points with lower numerical values, which tend to occur more frequently, are encoded using fewer bytes. UTF-8 is capable of encoding all 1,112,064 valid character code points in Unicode using one to four one- byte (8-bit) code units. Defined by the Unicode Standard, the name is derived from Unicode (or Universal Coded Character Set) Transformation Format – 8-bit. UTF-8 is a variable-length character encoding standard used for electronic communication.
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