Text Diff Checker

How to use the Text Diff Checker

1. Paste your original text into the left box and the changed text into the right box.
2. Click "Compare" to run a line-by-line diff.
3. Removed lines are highlighted red on the left, added lines are highlighted green on the right.
4. Use the swap button to quickly reverse which text is "original" and which is "changed".

Why use ZillaKit's Text Diff Checker?

Comparing two versions of a document, config file, or piece of code by eye is slow and error-prone. ZillaKit's text diff checker uses a classic longest-common-subsequence algorithm to compute an accurate line-by-line comparison and displays the result as a side-by-side colored diff, so additions and removals are immediately obvious. Everything runs locally in your browser — nothing you paste is uploaded anywhere, which matters when comparing sensitive drafts, contracts, or proprietary code. It is free, requires no signup, and handles large documents (well beyond typical page lengths) quickly thanks to an efficient diff implementation.

FAQ

Is the diff line-based or character-based?

This tool computes a line-based diff, meaning it compares whole lines against each other rather than individual characters, which is typically clearer for prose and code.

What algorithm powers the comparison?

The tool implements a longest common subsequence (LCS) algorithm, the same principle behind most version-control diff tools.

Can I compare very large documents?

Yes, the diff engine is optimized to handle large texts (well over 1MB) efficiently since it runs entirely client-side.

Is my text uploaded anywhere?

No. All comparison happens locally in your browser. Your text is never sent to a server.

How do I quickly reverse the comparison direction?

Click the swap button between the two text boxes to instantly swap the original and changed text.