diff
What is a .diff file?
text/x-diff
A .diff file records the difference between two versions of one or more text files. The unified format — the default almost everywhere — names the old and new files on `---` and `+++` lines, then lists hunks introduced by `@@ -old,count +new,count @@` in which context lines are unprefixed and changed lines are prefixed with `-` or `+`. Older context and normal diff formats exist but are rarely produced today.
How to use a .diff file
Use an example .diff file to test diff parsers, syntax highlighters, and merge tooling — verifying hunk-offset arithmetic, correct handling of context lines that begin with a space, and behaviour on files whose changes include trailing-whitespace or line-ending differences.
Download example .diff files
- Unified Diff - Single Hunk, Single FileOne added guard line in a shell script, rendered as a POSIX `diff -u` with three lines of context and timestamped ---/+++ headers. The smallest complete unified diff, and the baseline the context-format and normal-format twins in this group encode identically.
- Context Diff - Classic *** / --- FormatThe same change as the unified twin, emitted in the pre-unified context format: `*** before` and `--- after` blocks separated by a row of asterisks, with `!`, `+` and `-` change markers. Parsers that assume every diff starts with `---`/`+++` misread this one as a unified diff with no hunks.
- Normal Diff - ed-Style Change CommandsThe default output of bare `diff`: ed-style commands such as `3a4` with `<` and `>` bodies and no file headers at all. Tooling that identifies diffs by looking for `---`, `+++` or `@@` cannot even tell this is a diff, which is exactly what makes it a useful negative fixture.
- Unified Diff - Reverse of the Single-Hunk DiffThe exact inverse of the single-hunk fixture: the same edit expressed as a deletion instead of an insertion. Applying both in sequence must return the file to its original bytes, which makes this the fixture for `patch -R` and for revert paths.
- Unified Diff - Several Hunks in One FileOne TypeScript module edited in 2 places at once, so the hunks are far enough apart not to merge. Use it to check that a parser advances its line cursor by the hunk header rather than by counting emitted lines.
- Unified Diff - Three Files in One StreamThree unrelated files changed in a single diff stream, with no `diff --git` lines to mark the boundaries — the only separator is the next `---` header. Splitters that key on `diff --git` see one file here instead of three.
- Unified Diff - New File Against /dev/nullA file created from nothing: the old side is `/dev/null` and the hunk header carries the zero-length range `-0,0`. Parsers that compute a 1-based start line from the old range produce line 1 instead of line 0 unless they special-case a zero count.
- Unified Diff - Deleted File Against /dev/nullThe mirror of the added-file fixture: every line is a deletion and the new range is `+0,0`. A renderer that writes an empty file instead of unlinking it, or that reports the change as a truncation, fails this one.
and 19 more in the library.