What is Text Diff? Complete Guide with Examples
A text diff (short for 'difference') is the result of comparing two versions of text to identify what changed between them. Diff algorithms detect additions, deletions, and modifications at the line or character level, and present the changes in a visual format using color coding—typically green for additions and red for deletions. Diff tools are fundamental to version control, code review, content editing, and legal document comparison.
How Does Text Diff Work?
Diff algorithms find the Longest Common Subsequence (LCS) between two texts, then derive the minimal set of insertions and deletions needed to transform one text into the other. The Myers diff algorithm is the most widely used, running in O(ND) time where N is the total length and D is the edit distance. The output is presented in unified or side-by-side format, with context lines surrounding each change to help readers understand the modification.
Key Features
- Line-by-line and character-level comparison for precise change detection
- Side-by-side and unified diff view modes for different reading preferences
- Color-coded output highlighting additions (green), deletions (red), and modifications (yellow)
- Whitespace-aware comparison with options to ignore trailing spaces, indentation changes, or blank lines
- Syntax-aware diffing that understands code structure for more meaningful comparisons
Common Use Cases
Code Review
Developers review pull requests by examining diffs that show exactly what code changed, making it easy to spot bugs, style issues, and logic errors in new or modified code.
Content Editing
Editors compare document versions to see what an author changed between drafts, track revisions, and ensure all requested changes were properly implemented.
Configuration Auditing
System administrators compare configuration file versions to identify what changed between deployments, debug issues caused by config modifications, and maintain change documentation.