Prettier "Code style issues found" with --check in CI

By Kaveh Alemi·Latchkey

Prettier --check lists files whose formatting differs from Prettier's output, then exits 1. It does not change files; it only reports that they are not formatted.

What this error means

The format check prints "Checking formatting..." then "[warn] Code style issues found in the above file(s). Run Prettier with --write to fix." and exits with code 1.

Checking formatting...
[warn] src/app.tsx
[warn] src/utils/format.ts
[warn] Code style issues found in the above file(s). Run Prettier with --write to fix.

Common causes

Files were committed without running Prettier

The listed files differ from Prettier's canonical output, so --check flags them and fails the job.

A Prettier version or config change shifted formatting

A different Prettier version or a changed setting (printWidth, singleQuote) reformats code differently than what is committed.

How to fix it

Format the files and commit

1. Run Prettier with --write across the repo.
2. Commit the reformatted files.
3. Re-run --check to confirm a clean exit 0.

npx prettier --write .
npx prettier --check .

Pin the Prettier version across local and CI

Lock Prettier so local --write and CI --check agree on formatting.

npm install --save-dev --save-exact prettier@3.3.3

How to prevent it

• Run prettier --write in a pre-commit hook.
• Pin Prettier to an exact version in devDependencies.
• Keep one .prettierrc shared by local and CI.

Frequently asked questions

Related guides

References

• Node.js documentation
• npm CLI documentation
• GitHub Actions documentation