Big5 is the dominant legacy encoding for Traditional Chinese, used in Taiwan, Hong Kong, and Macau before UTF-8 became standard. It stores the thousands of Traditional Chinese characters as two-byte sequences while keeping ASCII single-byte.

How many bytes per character?

ASCII characters take one byte (0x00 to 0x7F). Each Chinese character takes two bytes: a lead byte from 0x81 to 0xFE and a trail byte from 0x40 to 0x7E or 0xA1 to 0xFE, leaving a gap in the trail range.

Why might a character be unmapped?

Big5 covers Traditional Chinese and ASCII, not Simplified-only characters, many rare ideographs, emoji, or other scripts. Those have no Big5 bytes and are flagged with ?? when encoding so nothing is silently lost.

Is Big5 the same as GBK?

No. GBK / GB2312 encodes Simplified Chinese with a different byte layout, and Big5 encodes Traditional Chinese. The same logical character generally has different bytes in each, so the encoding name must travel with the data.

Does the conversion happen locally?

Yes. The Big5 table is built in your browser from the native decoder and used locally for both encoding and decoding. No text is sent to any server.

Big5 Encoder/Decoder

Big5 is the established legacy encoding for Traditional Chinese, long used across Taiwan, Hong Kong, and Macau. It keeps ASCII as single bytes and stores each Traditional Chinese character as a two-byte pair. This tool encodes Traditional Chinese text into Big5 hex bytes and decodes Big5 bytes back into text.

How it works

ASCII characters 0x00–0x7F are stored as one byte. Every Chinese character is two bytes: a lead byte in 0x81–0xFE followed by a trail byte in 0x40–0x7E or 0xA1–0xFE. The gap between 0x7F and 0xA0 in the trail range is what keeps Big5 distinguishable from other double-byte schemes.

To use the exact Big5 mapping, the tool enumerates the single-byte range and all valid lead/trail pairs, decodes each pair with the browser’s native Big5 decoder, and builds a character-to-bytes map. Encoding looks each input character up in that map; decoding passes the hex bytes through the native decoder.

Example and notes

"中文" encodes to a4 a4 a4 e5 — two characters, each a two-byte pair, with 中 as A4 A4 and 文 as A4 E5.
Big5 is for Traditional Chinese; Simplified-only characters and many rare ideographs are not in the table and will be flagged as unmapped.
Several Big5 extensions exist (Big5-HKSCS adds Hong Kong characters). This tool follows the encoding your browser’s standard Big5 decoder implements; for full Unicode coverage, use UTF-8.