How to compare two texts
- Paste the original version into the left box.
- Paste the new or edited version into the right box.
- Press Compare. Lines that exist only in the original are shown in red with a minus sign; lines that exist only in the new version are shown in green with a plus sign.
- Use the options to ignore spacing or capital letters, or hide unchanged lines to focus on what changed.
How the comparison works
The tool uses a longest common subsequence (LCS) algorithm — the same idea behind the diff command used by programmers and by version-control systems such as Git. It finds the largest set of lines that appear in both texts in the same order, treats those as unchanged, and marks everything else as added or removed. This gives a minimal, readable list of changes rather than flagging every line after the first difference.
A line that was edited shows up as one removed line (the old wording) followed by one added line (the new wording), so you can read the before and after next to each other.
When a diff checker saves time
- Contracts and agreements: check exactly what the other side changed in a revised draft before you sign.
- Essays and articles: see what an editor or a grammar tool rewrote.
- Code and configuration files: spot the one changed setting that broke something.
- Lists and data exports: find which items were added or dropped between two versions of a list.
- Website copy: compare an old and new version of a page before publishing.
Getting cleaner results
Text copied from PDFs or emails often contains extra spaces at the end of lines, which makes otherwise identical lines look different. Tick Ignore leading/trailing spaces to skip those. If capital letters don’t matter for your comparison, tick Ignore case as well.
The tool compares lines. If your text is one long paragraph, a single changed word marks the whole paragraph as changed. For prose, put each sentence on its own line first for a more precise result.
Privacy
Many online diff tools send both texts to their server. This one does not: the comparison runs entirely in your browser, which makes it safe for confidential documents and private code.
Frequently asked questions
Is there a size limit?
Texts of a few thousand lines compare in well under a second. Very large files (tens of thousands of lines on both sides) may take a few seconds on slower devices.
Can I compare Word or PDF files?
Copy the text out of the document and paste it into each box. Formatting such as bold or fonts is not compared — only the text itself.
Does it show changes within a line?
This version compares whole lines. A changed line appears as a removed line followed by an added line so you can see both versions together.
Is my text uploaded?
No. The comparison runs locally in your browser, so both texts stay on your device.
What does “swap sides” do?
It switches the original and changed text, which reverses what is shown as added and removed.