Text Diff Checker
Compare two texts side-by-side.
Overview
Compare two pieces of text side by side and see exactly what changed. Additions are highlighted in green, deletions in red, and unchanged context is shown in muted text. The view can switch between unified (one column with markers) and split (two columns) layouts.
Developers reviewing pull requests outside of git, technical writers reconciling two drafts, editors checking copy edits, contract reviewers tracking line-by-line redlines, and anyone proofreading the difference between two versions of a paragraph all reach for a text diff. It's faster and clearer than reading both files end to end.
How it works
Under the hood, a text diff runs a longest-common-subsequence (LCS) algorithm over the lines (or characters, or words) of both inputs. The LCS represents the unchanged portion; everything not in the LCS is either added (present only in the right side) or deleted (present only in the left). Different tools tune the granularity — character, word, or line diffs each highlight different kinds of change.
Most diffs use Myers' 1986 algorithm or a variant like patience diff for cleaner-looking results on code.
Examples
Left: Right:
The quick brown fox The slow brown fox
jumps over the lazy jumps over the sleeping
dog. dog.
Diff (unified):
The -quick +slow brown fox
jumps over the -lazy +sleeping
dog.
FAQ
Word diff or line diff — which should I use?
Use line diff for code, configuration files, and structured data. Use word diff for prose where small wording changes matter more than line boundaries.
Does it ignore whitespace?
Most modes offer an "ignore whitespace" toggle. Useful for code reviews where indentation changed without semantic effect.
Can I diff three versions at once?
Two-way diff compares two inputs. For three-way comparisons against a common ancestor, use the Text 3-Way Merge tool.