Diff Checker
A free, browser-based text comparison tool. Paste two versions of any text into the side-by-side editor and instantly see every addition, deletion, and change highlighted — nothing is sent to a server.
Diff Checker
Compare two texts side by side with character-level highlighting
How to use Diff Checker
- 1 Paste the original text into the left panel — this is the "before" version.
- 2 Paste the modified text into the right panel — this is the "after" version.
- 3 The diff is computed automatically. Lines with changes are highlighted: green for additions, red for deletions, and yellow at the character level for inline edits.
- 4 Review the similarity score and line statistics at the top to get a quick overview of how much has changed.
- 5 Scroll through the comparison to identify specific changes. Use the highlighted character regions to see exactly which words or characters were modified within a line.
Features
Common use cases
Developers and code reviewers use it to compare snippets of code, configuration files, or scripts when a full git diff is unavailable — for example, comparing text copied from two different environments or systems.
Writers and editors use it to compare two drafts of a document, article, or email and identify what changed between revisions without enabling tracked changes in a word processor.
Legal and compliance teams use it to compare contract drafts, policy documents, or terms-of-service versions to identify what clauses were added, removed, or modified between versions.
SEO and content teams use it to compare page copy before and after edits, or to verify that translated content matches the structure of the original without unintended additions or omissions.
Students and researchers use it to compare their own drafts against source material to verify accurate quotation and avoid paraphrasing errors.
Frequently asked questions
What does the Diff Checker do?
Diff Checker compares two blocks of text and shows you the differences line by line, with character-level highlighting so you can see exactly what changed, was added, or was removed. It uses a longest common subsequence (LCS) algorithm, the same approach used by tools like git diff, to produce an accurate and minimal diff.
Is my text uploaded anywhere?
No. The diff is computed entirely in your browser using JavaScript. Your text never leaves your device, making it safe to compare source code, legal documents, configuration files containing credentials, or any other sensitive content.
Is the Diff Checker free?
Yes. Diff Checker is completely free to use with no sign-up, no rate limits, and no file size caps beyond what your browser can handle in memory.
What can I compare with this tool?
Any plain text — source code, configuration files, contracts, articles, JSON, YAML, logs, email templates, and more. The tool operates at the text level, so it works regardless of what the content represents. It is not designed for binary file comparison.
How is the similarity score calculated?
The similarity score is derived from the ratio of unchanged content to total content. A score of 100% means the texts are identical. A score near 0% means almost everything has changed. It gives you a quick sense of the overall scale of the diff before reading the details.