Text Comparison and Diff Checking Guide
Our text diff checker compares two blocks of text side by side, highlighting every addition, removal, and modification with color-coded markup. It's an essential tool for writers reviewing edits, developers comparing code snippets, students checking document versions, and anyone who needs to quickly identify what changed between two text versions.
How Text Diff Works
Our diff algorithm compares texts line by line using a longest common subsequence (LCS) approach — the same underlying technique used by Git, Unix diff, and code review tools. Lines that appear in the first text but not the second are marked as removed (red). Lines in the second but not the first are marked as added (green). Lines present in both are unchanged (gray). This gives an accurate picture of exactly what was added, removed, or modified.
Common Use Cases
Document revision tracking: Compare a draft sent to an editor vs. the returned version to see every change. Code review: Compare two versions of a function or configuration file without using git. Plagiarism checking: Compare student submissions against reference material. Contract comparison: Identify clause changes between versions of a legal document. SEO content updates: Compare original and revised copy to verify all changes were applied correctly.
Diff vs. Track Changes
Microsoft Word's "Track Changes" and Google Docs' version history show changes in-document. Our diff checker is format-agnostic — paste raw text from any source. It's particularly useful for comparing code, config files, or content from systems that don't have built-in version control.
Using Our Free Text Diff Checker
Paste the original text in the left panel and the modified text in the right panel. Click Compare (or it may update automatically). Additions are highlighted in green, removals in red, and unchanged lines in gray. Scroll both panels simultaneously to navigate long documents.
Frequently Asked Questions
How does the diff checker work?
It compares texts line by line using a longest common subsequence algorithm. Lines only in the left are marked removed (red), lines only in the right are marked added (green), and shared lines are unchanged (gray).
Can I compare code with the diff checker?
Yes. The diff checker is format-agnostic — paste any text including source code, JSON, HTML, SQL, or configuration files. It compares line by line regardless of content.
What is the difference between line-by-line and word-by-word diff?
Line-by-line diff marks entire lines as added or removed — better for code and structured content. Word-by-word diff highlights specific words within lines — better for prose and documents.