Why does every line show as changed in my diff?

Almost always a line-ending mismatch: Git is checking out CRLF while Prettier writes LF, or the reverse. Add * text=auto eol=lf to .gitattributes and run git add --renormalize . once.

Should Windows developers use crlf?

No. Every current Windows editor handles LF, and crlf creates cross-platform diff noise for everyone else. Keep lf and let .gitattributes enforce it.

What does auto actually do?

It preserves whichever ending the file already uses, judged from its first line. It was the pre-Prettier-2 default and is the cause of most historical line-ending churn.

`endOfLine` — line endings, and the Windows diff problem this option was created to end

The Prettier End Of Line option

endOfLine sets the line-ending characters Prettier writes. The default lf is the right answer on every platform including Windows, and the reason is that line endings are a repository-level decision that should never vary by who checked the code out.

Which end of line characters to apply.

Prettier's own description, from the official options documentation

Default: "lf"
Type: choice
CLI flag: --end-of-line
Allowed values: lfcrlfcrauto

What the four values do

lf (default) — a single \n. The Unix convention and the one Git stores internally.
crlf — \r\n. The Windows convention.
cr — a bare \r. Classic Mac OS, effectively obsolete; included for completeness.
auto — keep whatever the first line ending in the file already uses.

Why the default is lf everywhere

Before Prettier 2, the default was auto, and the result was a recurring and thoroughly unpleasant bug. A Windows developer would check out a repository with Git's core.autocrlf converting endings to CRLF, run Prettier, and produce a diff in which every line of every touched file appeared modified — because every line ending had changed.

Prettier 2 changed the default to lf precisely to stop that. With lf, the file on disk has the same bytes regardless of platform, so the diff shows only real changes.

Windows is not a reason to choose crlf. Every current Windows editor, and Notepad since 2018, reads LF files correctly. The convention costs nothing on Windows and saves a great deal everywhere else.

Getting Git to agree

Setting endOfLine alone is not enough if Git is still converting on checkout. The reliable fix is a .gitattributes file, which applies to everyone who clones the repository rather than depending on each developer's local configuration:

* text=auto eol=lf

.gitattributes — normalise in the repository, LF in the working tree.

With that in place, Git stores LF and checks out LF on every platform, and Prettier's lf setting agrees with it. If you add this to an existing repository you will need one normalising commit — git add --renormalize . — and it will be large.

When to use crlf or auto

Use crlf only if something downstream genuinely requires it — certain Windows-only build tools, or files consumed by legacy systems. Scope it with an overrides block rather than setting it globally.
Use auto only for a repository that already contains a deliberate mix and that you are not ready to normalise. It is a way of postponing the decision, not making one.
Otherwise leave it at lf and add the .gitattributes line.

Common mistakes

Setting endOfLine but not .gitattributes, so Git converts on checkout and Prettier converts back on save.
Choosing crlf because the team uses Windows. It is not necessary and it exports the problem to everyone else.
Normalising line endings in a commit that also contains real changes, which makes the real changes impossible to find.
Leaving ESLint’s linebreak-style rule enabled, which will disagree with Prettier on at least one machine.

Use it in .prettierrc

Drop endOfLine into your Prettier config file:

{
  "endOfLine": "lf"
}

Try it in the generator

Allowed values

lf: Line Feed only (\n), common on Linux and macOS as well as inside git repos
crlf: Carriage Return + Line Feed characters (\r\n), common on Windows
cr: Carriage Return character only (\r), used very rarely
auto: Maintain existing (mixed values within one file are normalised by looking at what's used after the first line)

Common questions

Why does every line show as changed in my diff?: Almost always a line-ending mismatch: Git is checking out CRLF while Prettier writes LF, or the reverse. Add * text=auto eol=lf to .gitattributes and run git add --renormalize . once.
Should Windows developers use crlf?: No. Every current Windows editor handles LF, and crlf creates cross-platform diff noise for everyone else. Keep lf and let .gitattributes enforce it.
What does auto actually do?: It preserves whichever ending the file already uses, judged from its first line. It was the pre-Prettier-2 default and is the cause of most historical line-ending churn.

Other Global options

Generated from Prettier 3.9.6.

endOfLine — line endings, and the Windows diff problem this option was created to end