Text Diff Checker
Paste two versions and see what moved — including the changes you cannot see on screen, a space at the end of a line or a tab among spaces, which are the ones that waste an afternoon.
How to read it
Green lines were added, red lines were removed, and faded lines are the same in both. A line that was edited shows as one removed and one added, because the comparison works on whole lines: change a comma and the whole line is marked.
The differences you cannot see
This is the reason a page like this exists. Two files can look identical on screen, character for character, and still not match, because of something invisible:
- A space at the end of a line. Nothing shows it. It breaks string comparisons, fails tests, and survives copy and paste.
- Tabs instead of spaces. They line up the same way on screen and are entirely different characters.
The two tick boxes let you ignore trailing spaces and capitals, and the third makes spaces and tabs visible, so you can see what you are actually dealing with rather than guessing.
The one this page honestly cannot see
Windows ends a line with two characters where everything else uses one, and that difference breaks builds, checksums and comparisons while showing nothing on screen. It is the classic invisible difference — and a web page cannot detect it.
The reason is worth knowing. The moment text enters a box on a web page, the browser quietly converts every Windows line ending to a plain one. By the time any page can look at what you pasted, the difference has already been erased. Anywhere claiming to spot it from pasted text is not telling you the truth.
So if two files match here but your computer insists they differ,
line endings are the first thing to suspect — and you need
something that reads the files themselves rather than a page you
pasted into. git diff, or a desktop comparison tool,
will show it.
It compares lines, not words
A word-level comparison looks cleverer and is much harder to trust: it guesses which words correspond, and when it guesses wrongly the result is confidently wrong. Lines are unambiguous. If you want to see a change inside a long paragraph, put each sentence on its own line in both versions first and the comparison becomes useful again.
Both pieces of text stay here
Nothing is uploaded. That matters for this tool in particular, because the thing people most want to compare is two versions of a contract, a configuration file, or something else they would rather not hand to a website.
Frequently asked questions
Why is a line I only edited shown twice?
Because it compares whole lines. An edited line is the old one removed and the new one added - there is no third category. Splitting long paragraphs into one sentence per line makes the result much easier to read.
It says the texts differ but they look the same.
Then the difference is invisible. Tick 'show invisible characters' and look for a trailing space, a tab where you expected spaces, or a different kind of line ending. That is exactly the case this page is built for.
Can it tell me if the only difference is Windows line endings?
No, and nor can any other web page. The browser converts them to plain line endings the instant you paste, so the difference is gone before the page sees anything. If two files match here but your computer says they differ, that is the likely reason - use git diff or a desktop tool, which read the files themselves.
How large a file can I compare?
Up to about fifteen hundred lines on each side. Beyond that the comparison grows faster than the text does and the tab would hang, so it stops and tells you instead.
Is my text sent anywhere?
No. Both sides stay in your browser, which is the point - the documents people most want to compare are usually the ones they least want to upload.
Is my text sent anywhere?
No. Everything happens in JavaScript inside your own browser. Nothing is uploaded and nothing is saved - close the tab and it is gone.