Free Online Text Diff & Comparison Tool

Paste  ·  Compare  ·  Private

What is a text diff tool?

A text diff tool compares two versions of a text and shows exactly what changed — which lines were added, removed, or stayed the same. diffDash highlights changes line by line and character by character, making it easy to spot differences between two texts at a glance.

How do I use diffDash?

Paste your original text into the left box and your updated text into the right box. The diff appears instantly — no button to press. Use the filter badges above the result to show only additions, only deletions, or all unchanged lines. When you're done, click ↓ Download .patch to save the diff as a standard patch file you can share or apply later.

What do the colors and symbols mean?

Green rows marked with + are lines that appear in your modified text but not the original — they were added. Red rows marked with − are lines from the original that no longer exist — they were deleted. Dimmed rows are unchanged. Within changed lines, the specific characters that differ are highlighted more brightly, so you can pinpoint the exact edit without scanning the whole line.

Can I use this to compare code?

Yes. diffDash works on any plain text — source code, config files, JSON, Markdown, CSV, prose, or anything you can paste. It has no file-type restrictions. Paste both versions and the diff output shows insertions in green and deletions in red, with inline character-level highlights for lines that partially changed.

What does the .patch file contain?

The downloaded patch uses the unified diff format: lines starting with + were added, lines with − were removed, and lines with a space are unchanged context. This format is understood by Git, the patch command, and most code editors — you can apply it directly to the original file.

How does character-level highlighting work?

For lines that changed, diffDash runs a second diff at the character level using the LCS (Longest Common Subsequence) algorithm — the same technique used by Git's word-diff mode. This pinpoints exactly which characters were added or removed within a line, not just which lines changed, which is especially useful when comparing similar sentences or config values.

Is there a limit on how much text I can compare?

There is no hard limit. diffDash runs the diff algorithm entirely in your browser, so performance depends on your device. Texts up to tens of thousands of lines work smoothly on any modern machine — no server round-trip, no timeout.

Is my data private?

Yes. The comparison runs entirely in your browser using JavaScript. Your text is never sent to any server — making this a fully private online diff checker, safe for source code, internal documents, or anything sensitive.