UTF-8 Decoder Checklist

This article is part of a series, Decoding UTF-8.

Using the information in UTF-8 Format Basics, you should be able to write a correct decoder. However, it is very easy to miss small details. Aside from just extracing codepoints from the multi-byte format, it is important to check that your decoder rejects:

• Overlong encodings -- codepoints encoded in more bytes than necessary
• Codepoints in the surrogate range (U+D800 to U+DFFF, inclusive)
• Codepoints greater than U+10FFFF are rejected