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Free Diff Checker | Compare Text & Code Online | AuthenTools

Compare two blocks of text or code line-by-line, word-by-word, or character-by-character — 100% private, nothing is ever uploaded.

Runs entirely in your browser — your files are never uploaded to a server.

This tool processes your file entirely in your browser using WebAssembly. Nothing is uploaded to our servers.

How It Works

1. Choose Your File

Drag & drop or select the file you want to work with.

2. Processed in Your Browser

Everything happens locally on your device — your file is never uploaded anywhere.

3. Download Your Result

Get your finished file instantly, ready to save or share.

About Free Diff Checker | Compare Text & Code Online | AuthenTools

Compare two blocks of text or code and instantly see exactly what changed — added lines in green, removed lines in red, with line, word, or character-level precision. Everything runs locally in your browser: nothing you paste here is ever uploaded, logged, or stored on a server.

Switch between a side-by-side view (classic two-column comparison) and a unified inline view (git-style, one column). Toggle ignore-whitespace and ignore-case when formatting differences shouldn’t count as real changes, and collapse long unchanged stretches so a big file’s actual edits aren’t buried in noise.

When you need the diff outside the browser, copy it, download it as a plain .txt, or export a real unified .patch file compatible with git apply and other standard diff tools — no account or sign-up required.

Frequently Asked Questions

What's the difference between line, word, and character diff modes?

Line mode compares whole lines — best for code, config files, and structured text where you want to know which lines changed. Word mode highlights the specific words that changed within a line — better for prose and documentation edits. Character mode goes finer still, down to individual letters — useful for spotting a single typo or a one-character change like "color" vs "colour".

Does this diff checker send my text anywhere?

No. The comparison runs entirely in your browser using JavaScript — the text you paste is never uploaded, transmitted, or stored anywhere. You can even use it offline once the page has loaded.

Can I export the diff as a real patch file?

Yes. The "Download .patch" button generates a standard unified diff format patch, the same format produced by git diff and diff -u, and it can be applied with git apply or patch -p1 on the receiving end.

What does "ignore whitespace" actually ignore?

It treats differences in spacing — extra spaces, tabs, or leading/trailing whitespace — as insignificant, so two lines that are identical except for how many spaces separate words will show as unchanged. Combine it with "ignore case" if capitalization differences shouldn't count either.

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