Text Diff

Features

• Line-by-line comparison marking added, removed and unchanged lines
• Edits aligned by minimal difference (LCS), not whole-block marking
• Side-by-side panes with line numbers matching each original
• CRLF and LF line endings treated as identical — no walls of false diffs
• Very large inputs degrade gracefully with an explicit notice instead of freezing

How to use

1. Paste the original on the left and the revision on the right
2. The comparison updates as you type — no button needed
3. Green marks additions, red marks deletions, grey is unchanged

FAQ

The two texts look identical but a diff is reported. Why?

Usually trailing whitespace or line endings. CRLF and LF are already treated as equivalent here, but an extra trailing space is still a real difference — just one that is hard to spot by eye.

How are the changes aligned?

A longest common subsequence algorithm finds the largest matching run between the two sides and treats the rest as insertions and deletions. That means only genuinely changed lines are marked, instead of everything after the first difference.

What happens with very long texts?

Diffing is O(n×m), so very large inputs fall back to a coarse "all removed, then all added" result. The page says so explicitly when that happens — the output is still correct, just not aligned to the minimal edit.