Text Diff Checker Online — Free Side-by-Side & Unified Diff Tool
Text Diff Checker
Compare two text blocks and highlight exactly what changed.
Free online text diff checker. Paste two versions of any text, code, JSON, YAML, or SQL into the left and right panels and compare instantly. View changes in side-by-side split mode or classic unified diff mode. Highlights added, removed, and modified lines with optional word-level and character-level inline highlighting. Supports ignore whitespace and ignore case options. Export a standard .patch file or share results via a compressed URL. Runs entirely in your browser — no data is ever sent to a server.
Keywords: text diff, diff checker, diff viewer online, compare text online, online diff, unified diff, side by side diff, code diff, file compare, text compare, diff tool, patch generator, json diff, yaml diff, line diff, word diff
Tags: diff, compare, text, patch, changes, merge
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How to Text Diff Checker Online
Paste the original version of your text into the left input panel (ORIGINAL).
Paste the updated version into the right input panel (MODIFIED).
Click Compare or press ⌘↵ to generate the diff instantly.
Switch between Split view (side-by-side) and Unified view using the mode toggle.
Copy the standard unified diff patch with ⌘⇧C, download it as a .patch file, or share your diff via a compressed URL.
Text Diff Checker Features
Side-by-side split view with synchronized scrolling for easy visual comparison
Unified diff view with standard +/- line notation (compatible with git diff output)
Line-level diff with added/removed/context line highlighting
Word-level inline diff: highlights the exact words that changed within a modified line
Character-level inline diff: pinpoints single-character changes for precision review
Ignore whitespace option: strips leading/trailing and internal space differences
Ignore case option: performs case-insensitive comparison
Configurable context lines: show 1–50 surrounding lines for each change hunk
Similarity score: percentage similarity between both texts
Export standard unified diff (.patch format) compatible with git apply and patch
Shareable URLs: gzip-compresses both inputs into a URL for team sharing
Works entirely in your browser — no data is sent to any server
Frequently Asked Questions
- What is a text diff?
- A text diff (short for difference) is a tool that compares two versions of text and highlights exactly what changed between them. It shows added lines in green, removed lines in red, and modified lines with inline highlighting to show exactly which words or characters changed.
- Is this diff tool free?
- Yes, DevFlow Text Diff Checker is completely free with no usage limits. All diffing runs directly in your browser.
- Is my data safe?
- All diffing happens entirely in your browser using JavaScript. No data is ever transmitted to a server. Your text stays completely private on your machine.
- What is the difference between split and unified view?
- Split view shows the original and modified versions side-by-side in two columns, making it easy to compare changes visually. Unified view shows all changes in a single column with + and - prefixes, similar to the output of git diff. Both views have the same information presented differently.
- What does word-level diff mean?
- Word-level diff goes beyond showing which lines changed and highlights exactly which words changed within a modified line. For example, if you changed 'The cat sat' to 'The dog sat', word-level diff will show 'cat' as removed (red strikethrough) and 'dog' as added (green highlight) within the same line.
- Can I use this to generate a git patch file?
- Yes. The tool generates standard unified diff format (.patch) that is compatible with git apply and patch commands. Click 'Copy' to copy the patch to your clipboard, or 'Download .patch' to save it as a file.
- How does the similarity percentage work?
- The similarity score is calculated using the longest common subsequence (LCS) method. It counts the number of equal characters between the two texts and expresses it as a percentage: 100% means the files are identical, 0% means nothing in common. This helps you quickly gauge how much two versions differ.
- Does it work offline?
- Yes. Once the page loads, all diffing happens locally in your browser without any network requests. You can use the tool offline after the initial page load.