Text Diff Checker
Paste an original and a changed version to see every difference highlighted: additions in green, deletions in red. Compare by line, word or character.
- Runs in your browser
- No sign-up
- Free to use
Differences
How to use Text Diff Checker
- Paste the original text on the left and the changed text on the right, or open a file for each side.
- Choose how to compare: by line for code and lists, by word for prose, or by character for small edits.
- Tick the options to ignore differences in letter case or whitespace if they are not relevant.
- Select Compare and read the highlighted result, with a count of what was added and removed.
Text Diff Checker features
Three levels of detail
Line, word and character comparison to suit code, documents or single-line strings.
Inline change highlighting
In line mode, the exact words that changed within a modified line are also marked.
Ignore case and whitespace
Filter out differences that do not matter, such as trailing spaces or capitalisation.
Change summary
Totals of added, removed and unchanged lines or words.
Swap sides
Reverse the comparison with one click.
Private comparison
Both texts stay in your browser, which matters for contracts, code and confidential drafts.
When to use Text Diff Checker
- Seeing what an editor or colleague changed in a document.
- Comparing two versions of a config file or code snippet without a version-control tool.
- Checking a contract or policy revision against the previous draft.
- Verifying that two lists or data exports are identical.
Text Diff Checker FAQ
Which comparison mode should I use?
Line mode is best for code, configuration and lists, where each line is a unit. Word mode suits paragraphs of prose, where a reflowed paragraph would otherwise show as entirely changed. Character mode is for spotting tiny differences in short strings such as IDs or URLs.
What do the colours mean?
Green marks text that exists only in the changed version (added). Red with a strike-through marks text that exists only in the original (removed). Unmarked text is the same in both.
Why does a whole paragraph show as changed?
In line mode a paragraph without line breaks is a single line, so any edit marks the entire line. The changed words inside it are still highlighted; switch to word mode for a cleaner view of prose.
Can I compare files?
Yes. Use the Open button above each box to load a text file from your device. Binary formats such as Word or PDF need to be converted to text first.
Is my text uploaded?
No. The comparison runs entirely in your browser.
How a diff is computed
Comparing two texts means finding the smallest set of insertions and deletions that turns one into the other. The standard approach, published by Eugene Myers in 1986 and used by tools such as git, looks for the longest sequence of units that appear in both texts in the same order. Everything in that common sequence is unchanged; whatever is left over on one side is a deletion, and on the other an addition.
What counts as a unit determines how readable the result is. Comparing line by line keeps the output compact for structured text, while comparing word by word follows the way people edit prose. When a line has been modified rather than replaced, comparing the old and new line word by word shows precisely what changed inside it.