Diff Checker (Online Text Difference Tool)
Free online diff checker. Paste two texts to instantly check the differences line by line or word by word - ignore case or whitespace and copy the result, all in your browser.
A quick online diff checker: paste two versions of any text and instantly see what changed. Added lines show in green, removed in red, and you can switch to inline mode to highlight the exact words. Ignore case or whitespace and copy the diff in one click.
Unchanged
1
Added
3
Removed
2
Similarity
25%
Diff
- -The quick brown fox
- -jumps over the lazy dog
- +The slow brown fox
- +jumps over the lazy cat
- on a sunny morning.
- +New line at the end.
How to use it
Paste the original
Left pane. Samples are pre-loaded so you can see the output immediately.
Paste the modified version
Right pane - or use Swap sides to flip the two.
Choose a view and options
Unified (line by line) or Inline (word level), and optionally ignore case or whitespace.
Read and copy
Check the unchanged/added/removed counts and similarity score, then Copy diff to export the result.
What is it?
A text diff tool compares two versions of a text and highlights what changed. Line-level diffs treat each line as an atomic unit - the algorithm finds the longest common subsequence of lines and labels the rest as inserts or deletes; word-level (inline) diffs do the same over words, so you see edits inside a line. It's the same engine that powers git diff and code-review tools.
When to use it
Comparing two drafts of an article. Spotting changes between an old and new contract. Reviewing what someone edited in a shared doc when there's no track-changes. Code review and auditing a config file before deploy. Proofreading, where the inline word diff makes small wording changes jump out. Sanity-checking that a paste did not introduce stray invisible characters.
Common mistakes
Comparing texts with different line-ending styles (CRLF vs LF) - every line then appears as 'removed + inserted'; turn on 'ignore whitespace' to fix it. Pasting from a PDF where line breaks come from the layout, not the content. And expecting word-level detail in the unified view: switch to Inline mode for that.
FAQ
- How is the diff computed?
- A standard longest-common-subsequence (LCS) backtrack - the same idea behind git diff. It finds the minimal set of insertions and deletions to turn the left text into the right, then labels each line (or word) as unchanged, added or removed.
- What's the difference between unified and inline view?
- Unified shows the change line by line: added, removed and unchanged lines stacked with +/- markers. Inline merges both sides into one stream and highlights the exact words that changed - best for spotting a small edit inside a sentence.
- Can I ignore case or whitespace?
- Yes. 'Ignore case' treats Hello and hello as identical; 'ignore whitespace' ignores spacing and indentation. The original text is still displayed - only the comparison changes, so cosmetic differences stop drowning out the real ones.
- Why does every line show as removed and added?
- Usually mismatched line endings (Windows CRLF vs Unix LF) or trailing spaces, so no two lines match exactly. Turn on 'ignore whitespace', or normalise the line endings before pasting.
- Does it do a word-level diff?
- Yes - switch to Inline view for a word-level (token) diff within the text. The unified view stays line-level, like a classic code diff.
- What does the similarity score mean?
- It's the share of unchanged content: unchanged lines divided by unchanged plus the larger of added or removed. 100% means the texts are identical; a lower number means more was edited.
Text Diff
Compare two texts line by line or word by word, with a similarity score.
Try it out →