Free Text Diff Checker
Four situations where a diff saves you
Comparing two versions of a text is a surprisingly common need, and eyes are bad at it. A single changed number in a long document can sit unnoticed for years. This checker lines up the two versions, and marks what was added and what was removed. Here are four situations where it earns its place.
A contract that came back changed
A supplier sends a new draft and says there are only small edits. Paste the old and the new, and the changes jump out, including the small ones that matter, such as a changed payment term.
Your draft after an editor’s pass
See exactly what a colleague or a tool changed in your writing, then accept or reject each change with your own judgement.
Two versions of a config file
Find the one setting that differs between a working server and a broken one.
A translation against its source
Compare two revisions of a translated document to see what was updated between them.
How to read the result
Added text is highlighted in green. Removed text is shown in red with a line through it. Unchanged text stays plain. Read down the changes in order, and for each one ask whether it was intended. Because the comparison is shown in context, you can often see why a change was made, which makes it easier to judge.
By line or by word?
Compare by line suits things where each line stands on its own: code, lists, data, configuration files and poetry. It shows whole lines as changed, so a one-letter change marks the full line. Compare by word suits prose, where lines are just wrapped text. It points to the exact words that changed inside a long paragraph. If you are not sure, try by word for writing and by line for everything else.
The two ignore options
- Ignore case treats Apple and apple as the same, which helps when the only difference is capitalisation that does not matter.
- Ignore extra spaces stops changes in spacing and line wrapping from showing as differences, which is common when text was copied from different sources.
Turn them on to reduce noise, and off when the exact characters matter, as in code.
What a diff cannot tell you
Moved text shows up as a deletion in one place and an addition in another, because the tool compares in order and does not understand that a paragraph was relocated. A diff shows what is different, not whether the change is acceptable. For a legal document, it is a good way to find the changes but no substitute for having a lawyer read them. And it compares text only, so formatting changes such as bold and layout are not visible.
Getting clean input
The result is only as good as what you paste. To compare Word or PDF documents, copy the text out of each, or extract the PDF text first with PDF to text. For structured data, format both sides the same way first. Pretty-print two JSON objects with the JSON formatter, with keys sorted, and then compare line by line.
Reviewing someone's edits fairly
When a colleague edits your work, the diff lets you respond to specifics. Accept the changes that improve clarity, reject the ones that change your meaning, and explain the ones you disagree with using the exact lines. It also makes review faster for them, because they can see precisely what you changed in reply.
Versions you can trust
Keep dated copies of important documents so that a comparison is always possible later. A habit of saving a new version before every major edit, with the date in the file name, turns this tool into a very reliable history check.
Size limits and privacy
The comparison uses a longest common subsequence method, the same idea as version control tools, and it runs in your browser. Long texts work well when most of the content is the same. If both sides are very long and different everywhere, the comparison may be too heavy for a browser, so compare in sections. Nothing is uploaded, which makes it suitable for private drafts and confidential documents.
FAQ
Paste each version into the two boxes and click Find differences. Additions and removals are highlighted.
Yes. Tick Ignore case and Ignore extra spaces.
Copy the text out of each file and paste it in. For PDFs, PDF to text can extract the text first.
Long texts work fine when most of the content is the same. Very long texts with changes everywhere can be too large to compare in a browser, so compare them in sections.
No. The comparison runs in your browser.