What encoding is utf-8?

UTF-8 is a variable-length character encoding for Unicode; it can be used to represent any character in the Unicode standard, and the first byte in its encoding is still compatible with ASCII, making The original software that processes ASCII characters can continue to be used without or with only minor modifications.

UTF-8 (8-bit, Universal Character Set/Unicode Transformation Format) is a variable-length character encoding for Unicode. It can be used to represent any character in the Unicode standard, and the first byte in its encoding is still compatible with ASCII, so that the original software that processes ASCII characters can continue to be used without or with only a few modifications. Therefore, it has gradually become the preferred encoding for email, web pages, and other applications that store or transmit text.

Basic features

UCS characters U 0000 to U 007F (ASCII) are encoded as bytes 0×00 to 0x7F (ASCIⅡ compatible). This means that files containing only 7-bit ASCII characters are the same in both ASCII and UTF-8 encodings.

All UCS characters greater than 0x007F are encoded as a string of multiple bytes, each byte has a flag bit set. Therefore, it is impossible for ASCII bytes (0x00-0x7F) to be part of any other characters. The first byte of a multibyte string representing a non-ASCII character is always in the range 0xC0 to 0XFD and indicates how many bytes the character contains. The remaining bytes of the multi-byte string are in the range 0x80 to 0xBF. This makes resynchronization very easy and makes encodings borderless and rarely affected by missing bytes.

UTF-8 encoded characters can theoretically be up to 6 bytes long. However, 16-bit BMP characters can only be up to 3 bytes long. The arrangement order of Bigendian UCS-4 byte strings is predetermined. Bytes 0xFE and OxFF are never used in UTF-8 encoding.

Number of encoding bytes

UTF-8 uses 1~4 bytes to encode each character:

·One US-ASCIl character only Requires 1 byte encoding (Unicode range is U 0000~U 007F).

·Latin, Greek, Cyrillic, Armenian, Hebrew, Arabic, Syriac and other letters with diacritical marks require 2-byte encoding (Unicode range is U 0080 ~U 07FF).

·Characters in other languages ​​(including Chinese, Japanese and Korean characters, Southeast Asian characters, Middle Eastern characters, etc.) include most commonly used characters and use 3-byte encoding.

·Other rarely used language characters use 4-byte encoding.

UTF-8 encoding rules:

If there is only one byte, its highest binary bit is 0; if it is multiple bytes, its first byte starts from Starting from the highest bit, the number of consecutive binary bits with a value of 1 determines the number of bytes encoded, and the remaining bytes start with 10.

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