webutilkit

Text Diff Checker

Compare two blocks of text line by line and see what was added, removed, or unchanged.

How it works

The two texts are split into lines and compared using the same longest common subsequence technique behind most diff tools: it finds the longest run of lines that appears in the same order in both texts, then marks everything else as removed from the original or added in the changed version.

Reading the output

Unchanged lines are shown as-is, removed lines are marked -, and added lines are marked +. A line that was simply edited appears as a removed copy of the old version directly followed by an added copy of the new one.

Line-level, not character-level

This compares whole lines. Changing one word in a long line marks that entire line as removed and re-added, rather than highlighting just the word that changed.

Frequently asked questions

Is this a word-level or line-level diff?

Line-level. Each line is compared as a whole, so a one-character change on a long line shows that entire line as removed and re-added rather than highlighting the single character.

Is there a size limit?

Very large inputs fall back to a simpler comparison to keep the tab responsive, since precise line-matching cost grows with the product of both texts’ line counts.