Text Compare & Diff Checker
Compare two passages line by line and highlight what changed. Your work stays on this device whenever possible.
How to use Text Compare & Diff Checker
- Paste the first version into "Original text" and the edited version into "Changed text", or load either side with its "Open file" button (.txt, .md, .csv, .json, .xml or .html, up to 2 MB).
- Pick "Compare by": Lines for whole-row edits, Words for reworded sentences, or Characters for tiny typos.
- Choose "Result view" as Side by side or Unified, and tick "Ignore letter case" or "Ignore whitespace changes" to hide noise.
- Press "Compare text" and read the summary strip, which reports added, removed and unchanged counts.
- Use "Copy diff" or "Download" for a patch-style file, "Swap sides" to reverse direction, and "Use changed as original" to compare the next revision.
Worked example
Original: "The cat sat.", "On the mat.", "The end." on three lines; Changed: the same with "On the rug.". In Lines mode the summary reads 1 added · 1 removed · 2 unchanged. Word mode on "The cat sat." against "The dog sat." copies as The {+dog}{-cat} sat. with 1 added · 1 removed · 3 unchanged.
When to use this tool
- Seeing exactly what a colleague changed in a contract paragraph before accepting it.
- Confirming two configuration files differ by one setting only.
- Spotting a single swapped character between two copies of a licence key or URL.
Important limitations
Comparison is computed line-by-line or character-by-character using an in-memory Myers diff engine. Very large text passages (over 100,000 words) process locally in your browser memory.
Frequently asked questions
What does a copied diff look like?
Line mode starts with "--- original" and "+++ changed", then prefixes each line with "+ ", "- " or two spaces. Word and Character modes give inline text with {+added} and {-removed} markers. It is readable, but it is not a unified diff with @@ hunks that a patch program could apply.
Why does Character detail sometimes refuse my text?
Comparison fills a table of one side's tokens times the other's. If that product passes 2,000,000, the tool stops with a message. At Character detail that is roughly 1,400 characters per side; Lines mode handles far more.
What does "Ignore whitespace changes" do?
It collapses each run of whitespace to one space and trims the ends before comparing, so re-indented lines count as unchanged. The original spacing is still what you see on screen.
Why does an edited line show as one removal plus one addition?
The algorithm finds the longest common sequence and has no "modified" category, so a changed line is a deletion paired with an insertion. In the output the added line is listed just before the removed one.
Do Windows and Unix line endings matter?
Not in Lines mode. Carriage returns are normalised to newlines before splitting, so two files that differ only in line-ending style compare as identical. Other whitespace differences inside a line still count as changes unless the whitespace option is ticked.