Free Text Diff Checker | Compare Two Texts Side by Side

About This Tool

This diff checker compares two pieces of text line by line and highlights what's different. Lines that were removed show on the left in red; lines that were added show on the right in green. Lines that are the same appear in both columns without highlighting.

When is a diff checker useful?

Reviewing document edits — compare a draft before and after feedback to see exactly what changed.
Checking code changes — spot differences between two versions of a script or config file.
Proofreading — paste two versions of an article or email to find accidental deletions or additions.
Version history — if you saved two copies of a file and aren't sure what changed, this shows you instantly.

How it works

The tool splits both texts into lines and compares them using a longest common subsequence (LCS) approach — the same method used by tools like Git's git diff. Lines that appear in both versions are considered unchanged; everything else is flagged as added or removed.

Tips for getting the best results

For documents, make sure both versions use the same line breaks — some programs (especially on Windows vs. Mac) format line endings differently.
If you're comparing code, keep indentation consistent — a line with an extra space is treated as a different line.
For large documents, focus on the highlighted lines — unchanged lines are shown for context but don't need review.

Frequently asked questions

Is my text uploaded anywhere?

No. All comparison happens locally in your browser using JavaScript. Your text never leaves your computer — safe for confidential documents, code, and private content.

Can I compare very long documents?

Yes, though very large texts (thousands of lines) may take a moment to process. For extremely long files, consider breaking them into sections for faster comparison.

Does it detect changes within a line, or only whole lines?

This tool compares at the line level — if a single word in a long sentence changed, the whole line will be flagged. For word-level highlighting within a line, you'd need a more advanced diff tool.

How is this different from using Ctrl+F to search?

Ctrl+F finds specific words, but it won't show you what's different between two versions. A diff tool shows the complete picture of every change — additions, deletions, and unchanged context — all at once.