Diff Checker
Compare two texts and highlight the differences line by line.
Processed locally in your browserCompare two pieces of text and see exactly what changed with this free online diff checker.
Drag & drop a file here, or
Max 5MB
Drag & drop a file here, or
Max 5MB
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How to Use
Compare two pieces of text and see exactly what changed with this free online diff checker.
- Paste your texts. Enter the original text in the left panel and the modified text in the right panel. You can also use the swap button to reverse them.
- View the differences. The tool highlights added lines in green and deleted lines in red, with line numbers for easy reference. Unchanged lines are shown for context.
- Check the stats. A summary at the top shows the total number of additions, deletions, and unchanged lines so you can gauge the scope of changes at a glance.
- Copy the result. Use the copy button to grab the diff output for pasting into code reviews, documentation, or issue reports.
This diff checker uses the Myers algorithm — the same approach used by Git — to find the minimal set of changes between two texts. It works with any plain text: source code, configuration files, prose, CSV data, or SQL queries. Everything runs in your browser — no data is sent to any server.
Features
- ✓Line-by-line comparison
- ✓Color-coded additions/deletions
- ✓Line numbers
- ✓Change statistics
- ✓Swap inputs
- ✓Real-time comparison
Frequently Asked Questions
- What is a diff checker?
- A diff checker is a tool that compares two pieces of text and highlights the exact lines or characters that differ between them. It is widely used by developers, writers, and data analysts to quickly spot changes between two versions of a file, document, or dataset.
- How does text comparison work in a diff checker?
- Most diff checker tools use the Myers diff algorithm, which finds the shortest edit script needed to transform one text into another. The result is a list of unchanged lines, added lines, and deleted lines, making it easy to see precisely what changed between the two inputs.
- What are unified and side-by-side diff formats?
- Unified diff format shows both versions in a single column, marking additions with a "+" and deletions with a "-". Side-by-side format places the two texts in adjacent columns so you can read them in parallel. A diff checker may support one or both formats depending on the use case.
- What are common use cases for a diff checker?
- Diff checker tools are used to review code changes before merging pull requests, compare configuration files, verify document revisions, audit database exports, and detect unintended edits in content. Any workflow that involves two versions of the same text can benefit from a diff checker.
- Can a diff checker compare source code?
- Yes — a diff checker works on any plain text, including source code in languages like JavaScript, Python, CSS, HTML, and SQL. For best results, format your code first with our JSON Formatter, SQL Formatter, or HTML Formatter, then compare the versions in the diff checker.