1.\" $OpenBSD: utf8.7,v 1.4 2017/05/31 12:46:30 jmc Exp $ 2.\" 3.\" Copyright (c) 2017 Ted Unangst 4.\" All rights reserved. 5.\" 6.\" Redistribution and use in source and binary forms, with or without 7.\" modification, are permitted provided that the following conditions 8.\" are met: 9.\" 1. Redistributions of source code must retain the above copyright 10.\" notice, this list of conditions and the following disclaimer. 11.\" 2. Redistributions in binary form must reproduce the above copyright 12.\" notice, this list of conditions and the following disclaimer in the 13.\" documentation and/or other materials provided with the distribution. 14.\" 15.\" THIS SOFTWARE IS PROVIDED BY THE DEVELOPERS ``AS IS'' AND ANY EXPRESS OR 16.\" IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES 17.\" OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. 18.\" IN NO EVENT SHALL THE DEVELOPERS BE LIABLE FOR ANY DIRECT, INDIRECT, 19.\" INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT 20.\" NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, 21.\" DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY 22.\" THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT 23.\" (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF 24.\" THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. 25.\" 26.Dd $Mdocdate: May 31 2017 $ 27.Dt UTF8 7 28.Os 29.Sh NAME 30.Nm utf8 31.Nd UTF-8 text encoding 32.Sh DESCRIPTION 33UTF-8 is a multibyte encoding for Unicode text. 34It is the preferred format for non ASCII text. 35.Pp 36The length of a UTF-8 sequence varies depending on the encoded value. 37If the high bit of the first byte is zero, the sequence length is one and 38the value is the remaining seven bits. 39If the high bit is set, then the number of high bits set, followed by a zero 40bit, indicates the length of the sequence and the value is formed by combining 41the low bits of each byte. 42Continuation bytes all have the same format, with the top two bits set and 43unset, respectively, and six value bits. 44.Pp 45Unicode ranges and their encoding formats: 46.Bl -tag -width Ds 47.It 0x0 - 0x7f 48One byte. 490....... 50.It 0x80 - 0x7ff 51Two bytes. 52110..... 10....... 53.It 0x800 - 0xffff 54Three bytes. 551110.... 10...... 10...... 56.It 0x1000 - 0x10ffff 57Four bytes. 5811110... 10...... 10...... 10...... 59.El 60.Sh SEE ALSO 61.Xr ascii 7 62.Sh STANDARDS 63.Rs 64.%A F. Yergeau 65.%D November 2003 66.%R RFC 3629 67.%T UTF-8, a transformation format of ISO 10646 68.Re 69.Pp 70The Unicode Standard. 71.Sh CAVEATS 72Beware of overlong encodings. 73