Text Comparison Tool
Text 1
Text 2
Tip: press Ctrl/⌘ + Enter to compare
Online Text Comparison Tool - Accurate Difference Detection
The Online Text Comparison Tool highlights exactly what changed between two pieces of text. It aligns lines intelligently, marks the precise words that were added, removed or modified, and reports a clear similarity score — all processed locally in your browser, so your text never leaves your device.
How to Use
Type or paste text into the two panels, or upload a .txt, .md, .csv or .json file into either side. Use Swap to flip the two sides instantly.
Turn on 'Ignore case' or 'Ignore whitespace' to skip cosmetic differences and focus only on meaningful changes.
Results update live as you type, or press Ctrl/⌘ + Enter (or the Compare button). Heavy diffs run in a Web Worker so the page stays responsive.
Switch between Side-by-side and Unified views, read the similarity score and statistics, then copy or download the diff.
Key Features
An LCS diff aligns matching lines and inserts gaps for added or deleted lines, so a single inserted line never pushes everything out of sync — a true diff, not index matching.
Inside changed lines, the exact words that were added or removed are highlighted, so you instantly see what differs without scanning the whole line.
Both panels show line numbers in a gutter, making it easy to locate and reference every change.
Get an overall similarity percentage plus counts of added, removed and modified lines and totals for characters, words and lines.
Compare in two columns with synchronized scrolling, or switch to a single unified stream of changes — whichever reads best.
Optional toggles let you ignore letter case or whitespace differences to surface only the changes that matter.
Auto-compare updates as you type, with heavy processing offloaded to a Web Worker so large texts won't freeze your browser. Ctrl/⌘ + Enter triggers a compare anytime.
Load text directly from files (.txt, .md, .csv, .json, .log) and swap the two sides with a single click.
All comparison happens locally in your browser. Nothing is uploaded to any server, so even sensitive text stays on your device.
Popular Use Cases
Spot changes between versions, inspect merge conflicts and catch configuration drift across files.
Track revisions between drafts, catch typos and make sure every edit is intentional.
Compare contracts, reports and policies to verify exactly what changed between revisions.
Compare essay drafts, cross-check references and review datasets or research notes.
Line up source text against translations to make sure nothing is missing or altered.
Diff CSV or JSON exports and compare log output to pinpoint differences quickly.
Frequently Asked Questions
Is my text uploaded to a server?
No. The tool runs entirely in your browser using a Web Worker. Your text is never sent anywhere, so it's safe to compare confidential or sensitive content.
What's the difference between side-by-side and unified views?
Side-by-side shows the two texts in parallel columns with changes aligned row by row — ideal for seeing where things differ. Unified merges everything into one stream, marking removed lines with '-' and added lines with '+', similar to a Git diff.
How is the similarity score calculated?
It's based on a character-level diff: the proportion of characters that are unchanged relative to both texts, expressed as a percentage. 100% means the texts are effectively identical under your current options.
What do 'Ignore case' and 'Ignore whitespace' do?
'Ignore case' treats uppercase and lowercase as equal (e.g. 'Hello' = 'hello'). 'Ignore whitespace' ignores leading/trailing spaces and differences in spacing between words, so reformatting alone isn't flagged as a change.
Can I compare files instead of pasting text?
Yes. Use the upload button on either panel to load a .txt, .md, .csv, .json or .log file. You can also paste text directly or swap the two sides at any time.
Is there a limit on text size?
There's no hard limit. Because diffing runs in a Web Worker, even long documents stay responsive, though extremely large inputs may take a moment to process.
Whether you're reviewing code, proofreading drafts or checking document versions, this text comparison tool gives you precise, word-level results with a clear similarity score — fast, free and completely private in your browser.