invalid-utf8: File contains invalid UTF-8 bytes

What it catches#

File contains invalid UTF-8 bytes.

Bytes that are not valid UTF-8 in a file that is otherwise UTF-8. The message gives the byte offset of the first bad sequence and the count. The usual cause is a file saved as Latin-1 or Windows-1252 that contains an accented letter, a curly quote or a dash.

Why it matters#

Tools that decode and save the file replace those bytes with U+FFFD, which silently changes it.

Bad example#

$ grep -n -P '[^\x00-\x7F]' AGENTS.md | head -1
14:- Ask Ren� before changing the billing module.

The é in a name was written as the single byte E9 by an editor set to Windows-1252. An agent that decodes the file as UTF-8 reads U+FFFD there, and a tool that re-saves it writes the replacement character back, so the name is now wrong in the repository.

Good example#

14:- Ask René before changing the billing module.

Saved as UTF-8, é is the two bytes C3 A9.

How to fix#

Convert the file: iconv -f WINDOWS-1252 -t UTF-8 AGENTS.md > tmp && mv tmp AGENTS.md. Then set the editor's default encoding to UTF-8. If only one character is wrong, retype it.

Suppress or configure#

For one finding, put a comment on the line above it. The reason after -- is optional but worth writing:

<!-- asitis-disable-next-line invalid-utf8 -- why this one is fine -->

For a whole file:

<!-- asitis-disable-file invalid-utf8 -- why this file is an exception -->

For every file, turn it off or change its severity in .asitisrc.json:

{ "rules": { "invalid-utf8": "off" } }

A .asitisrc.json overrides entry limits a change to some paths, and a baseline (asitis lint --format json --write-baseline) accepts today's findings so only new ones fail the build.

Source#

RFC 3629: UTF-8, read on 14 October 2026.

invalid-utf8