Free Online Text Diff Checker

A text diff tool compares two passages line by line and highlights added (green), removed (red) and unchanged lines using a longest-common-subsequence algorithm.

Your data is processed entirely in your browser and never sent to any server.

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How to Use This Text Tool

  1. Paste the original text into the left input.
  2. Paste the updated text into the right input.
  3. Review the side-by-side view: green = added, red = removed, unchanged lines show in both columns.
  4. Edit either side to see the comparison update live.

What Is a Text Diff Checker?

Diff tools are the workhorse of version control, content editing and contract review. The standard algorithm — longest common subsequence (LCS) — finds the smallest set of insertions and deletions that transform Text A into Text B. The result reads exactly like "git diff" or "diff -u" output: stable lines in the middle, with markers showing what changed where.

This tool runs entirely in your browser, so you can compare sensitive content (contracts, internal docs, draft posts) without uploading anywhere. Side-by-side view shows the original on the left and the updated text on the right; both columns scroll together.

Edit either side to see the comparison update live.

Frequently Asked Questions

What diff algorithm does this use?
A longest-common-subsequence (LCS) algorithm — the same approach as Unix diff and git. It finds the smallest set of additions and removals that transform one text into the other.
Is it character-level or line-level?
Line-level. Each line is treated as an atomic unit, which is the most common and most readable diff format for prose and code.
Can I diff more than two texts?
No — standard diff compares exactly two inputs. For three-way merge you would need git or a dedicated merge tool.

Published by the WeGotEveryTool team. We build and test every tool in-house and update pages when the underlying spec, formula, or recommendation changes.

Reviewed: May 2026. Disclaimer: this tool is provided as-is for general informational use. For decisions with material consequences (medical, legal, financial, security) verify results against a qualified professional source.

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