UsefulTab
Side-by-Side Diff Viewer
Compare two texts in an aligned two-column view.
Paste two texts to compare them side by side
Paste an original and a changed version, then click Compare. The original shows on the left and the changed text on the right, aligned line-by-line — computed in your browser with nothing sent to a server.
Runs entirely in your browserCompare two texts side by side, locally
A side-by-side diff puts the original and the changed version in two columns and lines them up so you can read the change in place instead of as one interleaved stream. This tool aligns the two texts with a longest-common-subsequence algorithm — the same idea behind git diffs — so unchanged lines sit on the same row and only the real edits stand out. Removed lines appear on the left, added lines on the right, and each side carries its own line numbers. All comparison happens in your browser and neither text is uploaded to any server.
Common questions
How is this different from a unified (single-column) diff?
A unified diff interleaves added and removed lines into one stream with + and - markers. This side-by-side view keeps the original and changed text in separate columns and aligns them on the same rows, which makes it easier to read a change in context — especially for code and config.
How does the alignment work?
The tool splits both texts into lines and computes the longest common subsequence of lines. Shared lines are placed on the same row in both columns; a removed line gets a row with the left side filled and the right blank, and an added line gets a row with the right side filled and the left blank. This keeps unchanged lines from drifting out of alignment.
Is this a character-level or line-level diff?
It is a line-level diff. Each line is compared as a whole unit, which is the most useful view for code, config, and prose. A single edit inside a line appears as that line removed on the left and the new version added on the right.
Does whitespace matter?
Yes. Lines are compared exactly, including leading and trailing spaces, so two lines that differ only in whitespace are treated as different. Trim your text first if you want to ignore that.
Are my texts uploaded anywhere?
No. Both texts are compared entirely in your browser with JavaScript. Nothing you paste is uploaded or stored on a server.