Text Diff Checker

Key features

• Line-by-line comparison using the classic LCS algorithm, so moved blocks are matched intelligently rather than flagged as total rewrites.
• Added lines glow green with a + marker; removed lines glow rose with a − marker; unchanged lines stay dim.
• Stat tiles summarize additions, removals, unchanged lines and an overall similarity percentage.
• Handles up to 1,500 lines per side with a loading state for bigger inputs.
• Monospace, line-counted input panels make aligning two versions easy.
• Runs the entire diff computation inside your browser — the texts never leave the page.

How it works

1. 1

   Paste the original

   Put the older version in the left Original panel — the line count shows underneath.

2. 2

   Paste the changed version

   Put the newer version in the right Changed panel.

3. 3

   Hit Compare texts

   The LCS diff runs and the result panel appears with every line marked +, − or unchanged.

4. 4

   Read the stats

   The tiles quantify the change: how many lines were added, removed, untouched, and the similarity percentage between the two sides.

Tips for better results

• 💡The comparison is line-based: changing one word marks that whole line as changed. Clean, consistent line breaks give the clearest results.
• 💡If a copy-paste introduced trailing whitespace, normalize both sides first — the diff treats 'text ' and 'text' as different lines.
• 💡For code reviews beyond 1,500 lines, split the file and diff it in sections, or use git for the full history.
• 💡Use the similarity percentage as a quick 'how much actually changed' gauge between two drafts.

Frequently asked questions