Text Diff
Place the original on the left, the revision on the right, and hit Compare. Every added word lights up green, every removed word turns red — with counters that tally the changes at a glance.
Code Review
Spot changed lines
Document Editing
Track draft revisions
Config Files
Catch setting changes
Proofreading
Verify editor corrections
How It Works
1
Paste Both Versions
Put the original on the left and the revised version on the right. Each panel accepts text of any length.
2
Set Comparison Rules
Toggle "Ignore case" or "Ignore whitespace" to filter out cosmetic changes and focus on substantive edits.
3
Read the Diff
Hit Compare and scan the color-coded output. Green is new, red is gone, and the stat counters summarize the delta.
Best Practices
✅ Do
- Enable "Ignore whitespace" when comparing reformatted or re-indented text
- Use Swap to verify the diff reads correctly in both directions
- Compare small, focused sections rather than entire 50-page documents
- Check the stat counters before reading — they show the scale of changes
- Turn on "Ignore case" when capitalization differences are irrelevant
- Pair with Find & Replace to apply the changes you spot in the diff
❌ Don't
- Paste two completely unrelated texts — the diff will be mostly red and green noise
- Forget that the diff is word-level, not character-level — small typo fixes may highlight entire words
- Ignore the "Unchanged" counter — a high number confirms the texts are mostly the same
- Compare very large texts (50,000+ words) without expecting a brief pause
- Assume moved paragraphs will be recognized — the LCS algorithm is order-dependent
- Leave both panels empty and click Compare — nothing useful will happen
Tips by Use Case
Code Review
- Paste the old function on the left, the new one on the right
- Enable "Ignore whitespace" to skip formatting-only diffs
- Look for red tokens — those are the lines you lost
- Use this for quick checks; full PRs need a proper review tool
Document Editing
- Compare your first draft against the editor's version
- Turn on "Ignore case" if the editor re-capitalized headings
- Scan green highlights for new suggestions to accept or reject
- Count removed words to gauge how much was cut
Config Files
- Diff the production config against staging to catch drift
- Ignore whitespace to skip indentation differences in YAML/JSON
- A single red or green line often reveals the breaking change
- Swap panels to verify which environment has the newer value
Proofreading
- Paste the pre-proofread and post-proofread versions
- Every green word is something the proofreader added
- Every red word is something they cut — review before accepting
- The unchanged count confirms how much survived intact
Frequently Asked Questions
What algorithm does the comparison use?
The tool tokenizes both texts into words and whitespace runs, then builds a Longest Common Subsequence (LCS) table using dynamic programming. It backtracks through the table to classify each token as added, removed, or unchanged — the same core approach used by Unix diff.
What do the green and red highlights mean?
Green marks words that appear in the modified text but not in the original — they were added. Red with a strikethrough marks words present in the original but missing from the modified — they were removed. Unhighlighted text is shared by both versions.
How does "Ignore case" change the result?
When enabled, the comparison treats uppercase and lowercase letters as identical. "Hello" and "hello" are considered the same token. This is useful for catching substantive changes without being distracted by capitalization tweaks.
What does "Ignore whitespace" do exactly?
It collapses all consecutive whitespace — multiple spaces, tabs, mixed space-and-tab sequences — into a single space before comparing. This way, re-indented code or reformatted paragraphs won't flood the diff with noise.
Is there a way to compare code with this tool?
Yes. Paste the old version on the left and the new version on the right, then click Compare. Enabling "Ignore whitespace" helps when the only formatting changed. For true line-by-line code diffs, a dedicated code-review tool is more appropriate, but this handles quick spot checks well.
What does the Swap button do?
It moves the contents of the Original panel into the Modified panel and vice versa. This lets you quickly check the diff in the opposite direction — what was "added" becomes "removed" and the other way around.
Is there a size limit?
There is no hard cap. However, the LCS algorithm is O(m x n) in memory and time, where m and n are the token counts. Texts under 10,000 words each compare instantly; very large documents (50,000+ words) may take a few seconds depending on your device.
Does this work with non-English or Unicode text?
Absolutely. The tokenizer splits on whitespace, which works correctly for any script that uses spaces as word separators. For scripts without word-spacing (Chinese, Japanese, Thai), the diff operates at the character cluster level instead.
Related Tools
Two Versions, One Click
Paste both texts, tap Compare, and every difference jumps off the screen in green or red. No login, no file uploads — just instant clarity on what changed.
