A diff checker compares two versions of a text and highlights exactly what changed — which lines were added, removed, or modified. Whether you are reviewing code changes, comparing document versions, or checking configuration file differences, this tool gives you an instant visual diff without installing any software.
How to Use the Diff Checker
Finding differences between two versions of a text is a fundamental task in software development, document editing, and content review. Our free diff checker gives you an immediate visual comparison without any setup, installation, or account required.
Step 1: Paste the Two Texts
Paste the original (older) version of your text into the left panel and the modified (newer) version into the right panel. The tool accepts any plain text: source code, JSON, XML, Markdown, configuration files, prose documents, or anything else. There is no size limit for typical usage.
Step 2: Click Compare
Click the Compare button to run the diff. The comparison updates automatically as you type in either panel. A summary bar shows the number of lines added (green), removed (red), and unchanged (gray) so you can quickly gauge the scope of changes.
Step 3: Choose Your View
Use "Side by Side" view to see original and modified text in parallel columns — ideal when you need to see context around each change. Switch to "Unified" view for a compact single-column diff with + and - prefixes, similar to git diff output. Both views include line numbers.
Reading the Color Coding
Lines highlighted in green with a + prefix were added in the modified version. Lines in red with a - prefix were removed from the original. Unchanged lines appear without highlighting. The diff algorithm finds the minimal set of changes — the same approach used by git and most version control systems.
Common Use Cases
The diff checker is useful for reviewing code changes before a pull request, comparing configuration file versions, checking whether a document draft changed since last review, verifying API response differences between environments, and comparing translated documents for missing sections.
Frequently Asked Questions
Is the diff checker free?
Yes, completely free with no account required and no usage limits. All text comparison happens in your browser — your text is never sent to any server.
Is my text private when using this tool?
Yes. The diff algorithm runs entirely in client-side JavaScript. Nothing is uploaded or stored anywhere. You can use this tool safely with confidential code, contracts, or sensitive documents.
What is a diff and how does it work?
A diff (from 'difference') compares two versions of a text and identifies which lines were added, removed, or changed. This tool uses the Myers diff algorithm to find the minimal set of edits that transforms the original text into the modified text. Added lines appear in green, removed lines in red.
What is the difference between side-by-side and unified diff view?
Side-by-side view shows the original and modified text in two columns with changes highlighted, making it easy to see context around each change. Unified view shows a single column with + and - prefixes for added and removed lines, similar to git diff output in the terminal.
Can I compare code files with this tool?
Yes, this diff checker works with any plain text including source code, JSON, XML, HTML, CSS, SQL, configuration files, and prose. For code comparison, paste the content of each file into the respective text area.
How do line numbers work in the diff view?
Line numbers are shown for both the original and modified text in side-by-side view. For unchanged lines, both numbers increment. For deleted lines, only the original line number appears. For added lines, only the modified line number appears.