How does the diff algorithm work?

The tool uses the Myers diff algorithm to compute the shortest edit script between two texts. It identifies inserted lines, deleted lines, and unchanged lines, then renders them with color-coded highlighting in side-by-side or unified view.

Is it safe to paste sensitive data?

Yes. All comparison happens 100% client-side in your browser. Your text never leaves your device. There are no API calls, no server-side processing, and no storage.

Can I diff very large files?

Yes. The tool uses virtualized rendering, meaning only visible lines are rendered in the DOM. This allows it to handle files with thousands of lines smoothly without freezing the browser.

What is the difference between side-by-side and unified view?

Side-by-side view shows the original text on the left and the modified text on the right, making it easy to spot changes at a glance. Unified view interleaves both versions in a single column, which is more compact and similar to git diff output.

Does the tool support word-level diffs?

Yes. In addition to line-level changes, the tool highlights word-level differences within changed lines, making it easy to see exactly which words were added, removed, or modified.

Encoding & Data

Diff Viewer

Free online diff viewer and text comparison tool. Compare two text inputs side by side or in unified view with inline word-level highlighting. See additions, deletions, and modifications at a glance with diff statistics, changes-only filtering, and virtualized rendering for large files. Diff code, config files, JSON, YAML, or any text without installing software. 100% client-side, no data uploaded.

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Quick reference

Category: Encoding & Data
Runs in: Browser
Data stored: Nothing
Price: Free
Sign-up: Not needed

Browse categories

All features

Side-by-side and unified views
Diff statistics (additions, deletions, modifications)
Changes-only filtering
Virtualized rendering for large files
Word wrap support

What you can do

Compare two text files

Paste two versions of a document, config file, or code snippet to see exactly what changed: additions, deletions, and modifications.

Review code changes

Use side-by-side view to review diffs with line-level highlighting, or switch to unified view for a compact single-column layout.

Diff large files

Virtualized rendering handles files with thousands of lines without lag or freezing the browser.

Filter to changes only

Toggle changes-only mode to hide unchanged lines and focus on the diffs that matter.

Compare config across environments

Paste production and staging configurations side by side to spot environment-specific differences before deploying.

Private by design

Client-side
No sign-up
Free

Diff Viewer runs entirely in your browser tab. No data is uploaded, no server processes your input, and no account is required.

Specifications

View modes: Side-by-side, unified
Diff stats: Additions, deletions, modifications
Large file support: Virtualized rendering (thousands of lines)
Features: Word wrap, changes-only filter, line numbers
Input: Paste text or drag-drop files
Processing: 100% client-side, no upload

Frequently asked questions

Related keywords

diff viewertext comparisononline diff toolcompare text onlinecode diffside by side diffunified difftext diff checkerfile comparison toolcompare two filesgit diff viewerinline diffword difftext compare tooldiff checker