Text Diff Checker

Text Diff Checker puts two versions of the same text side by side and marks what changed. Added lines are highlighted in green, removed lines in red, and everything untouched is shown plain so the changes stand out. A summary above the result counts the additions, deletions and unchanged lines.

The comparison uses a longest-common-subsequence algorithm, the same approach that version control tools use. That matters because it finds the real alignment between the two versions rather than comparing line one to line one. Insert a paragraph at the top of a document and the tool reports one addition, not a file where every line moved.

Options let you ignore things that do not matter to you: leading and trailing whitespace, differences in capitalisation, or empty lines. You can also switch from comparing lines to comparing words, which is the better view when two paragraphs differ by a handful of words rather than whole lines.

• Line-by-line and word-by-word comparison
• Added, removed and unchanged content clearly marked
• Counts of additions, deletions and unchanged lines
• Options to ignore whitespace, case and blank lines
• Uses proper difference alignment, not naive line pairing
• Marks changes with words as well as colour, so colour is not the only signal
• Copy the summary of changes

The text diff checker is used by writers, developers, students, marketers and anyone else who needs the job done once without installing software. Common cases include:

• Checking what an editor changed in a draft
• Comparing two versions of a configuration file
• Spotting the difference between two copied lists
• Reviewing a rewritten paragraph before publishing
• Confirming that a copy and paste transferred everything