Diff Checker — Compare Two Texts Online
Compare two texts and highlight the differences line by line. Free online text comparison tool.
What is a Diff Checker?
A diff checker compares two pieces of text and highlights the differences between them. Lines that exist only in the original are marked as removed (red), and lines only in the modified text are marked as added (green).
Common uses
Comparing code versions, checking document revisions, verifying configuration changes, and finding differences between API responses.
About This Tool
The Diff Checker compares two blocks of text side by side, highlighting additions, deletions, and unchanged lines with color-coded markup. It is used by developers, writers, and QA testers to quickly identify exactly what changed between two versions of code, configuration, or content.
Key Features
- Line-by-Line Comparison — Compares text at the line level, highlighting added lines in green and removed lines in red for immediate visual clarity.
- Unified Diff Output — Displays changes in a standard unified diff format that developers recognize from git diff and patch workflows.
- Character-Level Highlighting — Within changed lines, highlights the specific words or characters that differ so you can spot single-character typos instantly.
- Browser-Based Processing — All comparison happens locally in your browser. Your code and text never leave your device.
- Free & No Signup — Use this tool as many times as you need without creating an account or paying anything.
Common Use Cases
- Comparing two versions of a configuration file to find what changed during a production incident
- Reviewing changes to a legal document or contract to confirm only the agreed edits were applied
- Checking differences between two SQL scripts or database migration files before deployment
- Verifying that a translation or localization file has all the same keys as the original English source
- Spotting accidental whitespace, encoding, or line-ending changes in source code or scripts
How to Use
Paste the original text into the left panel labeled Original and the modified text into the right panel labeled Changed. Click Compare to run the diff. Added lines appear highlighted in green and removed lines in red. Scroll through the results to review all changes.
Frequently Asked Questions
How does the diff algorithm work?
The tool uses the Myers diff algorithm, the same algorithm used by git. It finds the shortest edit script (minimum number of additions and deletions) needed to transform the original text into the modified text.
Does the diff check ignore whitespace?
By default, whitespace changes are included in the comparison. A single extra space or different line ending (CRLF vs LF) will appear as a change. This is intentional for code and configuration file accuracy.
Can I compare binary files or images?
No. This is a text diff tool and works with plain text, code, JSON, XML, and similar formats. Binary files produce meaningless output because they contain non-printable characters.
What is the difference between a unified diff and a side-by-side diff?
A unified diff shows a single view with + and - prefix markers for added and removed lines. A side-by-side diff shows original and modified text in two columns. Both convey the same information but side-by-side is often easier to read.
Related Tools
Workflow Links
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Before This Tool