Text Diff Checker
Paste two versions of a text and see exactly what changed, highlighted line by line or word by word.
When two versions of a document, contract clause, config file or article draft look almost identical, spotting the actual differences by eye is slow and error-prone. This diff checker compares both texts and highlights every change: deletions are struck through in red, additions are marked in green, and everything unchanged stays plain so your eye goes straight to what matters.
You can compare by lines — best for code, lists and configuration files — or by words, which is usually clearer for prose and shows edits inline within sentences. The comparison uses the same longest-common-subsequence approach as professional diff tools, and it all runs locally in your browser: neither version of your text is ever uploaded, making it safe for contracts, unpublished work and internal documents. Cleaning up formatting first with the line break remover can make prose diffs even easier to read.
How to use the Text Diff Checker
- Paste the original text into the left box.
- Paste the changed version into the right box.
- Choose Lines for code and lists, or Words for sentences and paragraphs.
- Click Compare. Additions appear in green, deletions in red strikethrough, with a summary count above the result.
Frequently asked questions
Should I compare by lines or by words?
Use line mode for code, CSV data, lists and configs, where each line is a meaningful unit. Use word mode for prose — it highlights changes inside sentences instead of flagging a whole paragraph as different because one word changed.
Is my text private?
Yes. Both texts are compared entirely in your browser with JavaScript. Nothing is uploaded, logged or stored, so the tool is safe for confidential documents and contracts.
How large can the texts be?
Up to 3,000 lines (or 3,000 words in word mode) per side, which covers most documents and source files. For bigger inputs, split the text into sections or use line mode, which consumes the limit more slowly.
Does the tool ignore whitespace or capitalization?
No — the comparison is exact, so a changed space or capital letter counts as a difference. That's usually what you want when reviewing edits. If case differences are noise for your comparison, normalize both texts first with the case converter.
What algorithm does the diff use?
It computes the longest common subsequence (LCS) between the two token sequences — the same family of algorithm used by git and classic Unix diff — then marks everything outside that common core as an addition or deletion.