Compare two blocks of text and see exactly what changed
Diffing two versions by eye does not scale. This checker aligns the two texts line by line, then within each changed line word by word, so a one-character difference does not look like a rewritten paragraph.
- Granularity
- Line and word
- Options
- Ignore whitespace, case
- Output
- Unified diff
Measured on Apple M4 Max: 41 ms line diff with word-level highlighting (2,000 lines, 2.5% changed) See the benchmarks
How to use it
- Paste both versions The left box holds the original and the right box the changed version. Either side can come from a file.
- Adjust the comparison Turn off whitespace sensitivity when a reindent is all that changed, and turn off case sensitivity when only capitalisation differs.
- Read the result Changed lines are marked in the side-by-side view, and a unified diff is available to copy straight into a commit message or a pull request description.
Questions people ask
How does the diff algorithm work?
It is a longest-common-subsequence comparison over lines, which is the same family of algorithm Git uses. When the two texts share large common blocks, the result is the minimal set of changes that explains the difference.
What is a unified diff?
The standard patch format with context lines and +/- prefixes, as produced by the diff command. It is what Git expects when you paste a patch, and it reads well in a pull request description.
Should I turn off whitespace sensitivity?
Yes, when a formatter or an editor has reindented the file and the logic is unchanged. Leave it on when whitespace carries meaning, such as in Python, YAML or a Makefile.
Is there a size limit?
No explicit limit, but the comparison is quadratic in the worst case. Text of a few hundred thousand lines is fine; a multi-gigabyte file is not what this is for.
Can I compare two files on disk?
Open them in a text editor and paste each into a box, or use a command line tool such as diff or git diff for very large files. This one is here for the moment when you need to compare something that is not in a repository.
Does the word-level view replace the line-level one?
No, and you want both. The line view shows which lines changed so you can navigate, and the word view narrows each changed line to the specific words that differ.
Where this earns its keep
Comparing a generated file with a template
A codegen output against the expected output shows you exactly which line drifted, instead of scrolling two files side by side looking for the difference.
Checking a config change
Before and after a settings edit, diffed, shows the one line that moved and whether the whitespace changed too.
Reviewing a response body
When a response changes shape between two environments, diffing the two payloads finds the missing field in a second.
Details that catch people out
A line diff marks a whole line as changed when a single character differs. Adding the word-level pass narrows the highlight to the words that actually differ, which is the difference between a readable review and a wall of red.
Guides that go deeper
- What a Useful Diff Looks Like 6 min read · Why line diffs are too coarse, when word-level highlighting helps, and how structural…
Last reviewed 2026-10-07. Every tool on DevSnap runs entirely in your browser, so whatever you paste here never reaches a server.