Windows-1251 is an 8-bitcharacter encoding, designed to cover languages that use theCyrillic script such asRussian,Ukrainian,Belarusian,Bulgarian,Serbian Cyrillic,Macedonian and other languages.

On the web, it is the second most-used single-byte character encoding (or third most-used character encoding overall), and most used of the single-byte encodings supporting Cyrillic. As of January 2024^[update], 0.3% of allwebsites use Windows-1251.^[1][2] It's by far mostly used for Russian, while a small minority of Russian websites use it, with 94.6% of Russian (.ru) websites usingUTF-8,^[3][4][5] and the legacy 8-bit encoding is distant second. In Linux, the encoding is known as cp1251.^[6]IBM uses code page 1251 (CCSID 1251 andeuro sign extended CCSID 5347) for Windows-1251.^{[7][8][9][10][11][12][13]}

Windows-1251 andKOI8-R (or itsUkrainian variantKOI8-U) are much more commonly used thanISO 8859-5 (which is used by less than 0.0004% of websites).^[14] In contrast toWindows-1252 andISO 8859-1, Windows-1251 is not closely related to ISO 8859-5.

Unicode (e.g. UTF-8) is preferred to Windows-1251 or other Cyrillic encodings in modern applications, especially on the Internet, making UTF-8 the dominant encoding for web pages. (For further discussion of Unicode's complete coverage, of 436 Cyrillic letters/code points, including forOld Cyrillic, and how single-byte character encodings, such as Windows-1251 andKOI8-R, cannot provide this, seeCyrillic script in Unicode.)

The following table shows Windows-1251. Each character is shown with itsUnicode equivalent and itsAlt code.

An altered version of Windows-1251 was standardised inKazakhstan as Kazakh standard STRK1048, and is known by the labelKZ-1048. It differs in the rows shown below:

Code Page 1174 is another variant created for theKazakh language, which matches Windows-1251 for theRussian subset of the Cyrillic letters. It differs from KZ-1048 by moving the Cyrillic letterShha from 8E/9E to 8A/9A.

Windows Latvian + Russian is a modification of Windows-1251 to support theLatvian language.

Windows Cyrillic + Finnish is a modification of Windows-1251 that was used byParatype to cover theFinnish language. This encoding is supported byFontLab Studio 5.^[18] This variant is missing the lettersŠ andŽ which are used in loanwords in Finnish and can be replaced by the digraphs SH and ZH.

RussianAmiga OS systems used a version of code page 1251 which matches Windows-1251 for theRussian subset of the Cyrillic letters, but otherwise mostly followsISO-8859-1. This version is known asAmiga-1251,^[19] under which name it is registered with theIANA.^[20]

• Latin script in Unicode
  • Cyrillic script in Unicode
• Unicode
• Universal Character Set
  • European Unicode subset (DIN 91379)
• UTF-8

• Kornai, Andras; Birnbaum, David J.; da Cruz, Frank; Davis, Bur; Fowler, George; Paine, Richard B.; Paperno, Slava; Simonsen, Keld J.; Thobe, Glenn E.; Vulis, Dimitri; van Wingen, Johan W. (1993-03-13)."CYRILLIC ENCODING FAQ Version 1.3". Retrieved2020-06-24.

• Windows 1251 reference chart
• IANA Charset Name Registration
• Unicode mappings of windows 1251 with "best fit"
• Universal Cyrillic decoder, an online program that may help recovering unreadableCyrillic texts with broken Windows-1251 or othercharacter encodings.

• Windows code pages

• Articles with short description
• Short description is different from Wikidata
• Articles containing potentially dated statements from January 2024
• All articles containing potentially dated statements