Lazy Compare - Online Diff Check
Paste two versions of a text and LazyCompare marks every difference — line by line, then character by character. A full diff check in one click.
Text 1
Text 2
What is a diff check?
A diff check — also written diffcheck or diff checker — lines up two versions of the same text and marks everything that was added, removed or rewritten. Instead of re-reading both copies and hoping you notice the change, the tool does the reading: it aligns the lines that still match, highlights the ones that no longer do, and then narrows down to the exact characters that differ inside a line.
How to run a diff check
Paste the original
Drop the version you started from into Text 1.
Paste the new version
Put the revised copy into Text 2. Both boxes are saved locally, so a refresh will not lose your work.
Compare
Added lines turn green, removed lines turn red, and the characters that changed inside a line are shaded.
Walk through the changes
Prev and Next jump from one difference to the next, and the counter tells you how many are left.
What this diff checker gives you
Line and character level
The comparison aligns lines first, then narrows to the exact characters that moved — so one renamed variable does not read as an entirely rewritten line.
Nothing leaves your browser
The diff is computed on your own device and your drafts are kept in local browser storage. No upload, no account, no copy of your text on a server.
Built for long files
With wrapping turned off, only the rows on screen are rendered — thousands of lines stay smooth to scroll through.
Jump straight to a change
Every difference is indexed, so you never scroll hunting for the one line that moved.
When a diff check saves you time
Config and environment files
Compare two .env or YAML files to find the single key that differs between staging and production.
Translation and locale files
Check that an English and a Vietnamese JSON file carry the same set of keys before shipping.
Draft revisions
See what an editor, a teammate — or an AI — actually changed in your copy.
Code without a repository
Compare two snippets pasted from a chat, a log or an answer online, when git diff is not an option.
Frequently asked questions
Is my text uploaded anywhere?
No. The comparison runs in your browser, and what you type is cached in your browser's own storage so you can pick up where you left off. It is never sent to a server.
How much text can I compare at once?
There is no fixed limit — the practical ceiling is your device's memory. For very large inputs, turn off Wrap text: rows are then rendered on demand and scrolling stays responsive.
Does it work on code as well as prose?
Both. The diff check works on any plain text: source code, JSON, CSV, logs, Markdown or ordinary writing. For an actual git patch file, use the Git diff viewer instead.