Free Diff Checker — Compare Two Texts Side by Side Online

"What changed?" is the most common question in software development, content editing, and data management. A diff checker answers it visually — paste two versions of any text, and see exactly what was added, removed, or modified, highlighted line by line.

Our free diff checker compares two texts side by side with color-coded highlights. Green for additions, red for deletions. No file upload, no account, everything runs in your browser. Safe for comparing code, contracts, configurations, and any sensitive text.

What Is a Diff Checker?

A diff (short for "difference") checker compares two versions of text and shows every change between them. It uses algorithms (typically the Myers diff algorithm or similar) to find the minimum set of changes that transforms version A into version B.

The output is a visual representation: unchanged lines appear normal, added lines are highlighted in green, and removed lines are highlighted in red. This makes it immediately obvious what changed between two versions.

How Diff Checking Works

1. Paste the original text in the left panel
2. Paste the modified text in the right panel
3. The tool instantly highlights all differences
4. Green = added content, Red = removed content

The comparison is line-by-line by default. Each line is compared independently, and the tool identifies which specific lines were added, removed, or changed.

When You Need a Diff Checker

• Code reviews. Compare the before and after of a code change. See exactly what a pull request modifies without scrolling through GitHub's interface.
• Document editing. Did the legal team change the contract? Paste both versions and see every word that was added or removed.
• Configuration management. Compare production and staging configs to understand what differs between environments.
• Content verification. After a find-and-replace operation, compare the original and modified text to verify only intended changes were made.
• Database records. Compare two JSON/XML records to find field-level differences.
• API responses. Compare API responses from different endpoints, environments, or time periods to identify changes.

How to Read a Diff

Green highlighted lines exist only in the right panel (new version). These are additions — content that was added.

Red highlighted lines exist only in the left panel (old version). These are deletions — content that was removed.

Unhighlighted lines are identical in both versions. These provide context — they help you locate where changes occur within the document.

Modified lines appear as a deletion (red, left) paired with an addition (green, right) at the same position. This represents content that was changed rather than purely added or removed.

This Tool vs. Git Diff

Git diff is powerful but limited to files tracked in a Git repository. This tool compares any two texts — emails, documents, API responses, database records, clipboard content. You don't need a repo, a terminal, or Git installed. Paste and compare.

For developers: this is the tool you reach for when the content isn't in Git. For non-developers: this is diff checking without needing to learn Git.

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Frequently Asked Questions

Can I compare code in any language?

Yes. The diff checker compares text, not code. It works with any programming language, markup, configuration format, or plain text. It does not syntax-highlight code, but it accurately identifies every line-level difference.

How large of a comparison can it handle?

The tool handles documents with thousands of lines efficiently. For extremely large files, there may be a brief processing delay, but the comparison will complete.

Does it compare words within lines or just full lines?

The comparison is line-based. It identifies which lines differ between the two versions. Within changed lines, the entire line is highlighted rather than individual changed words.

Can I compare files?

The tool compares text content. Copy and paste content from any file — text, code, CSV, JSON, XML, config files — into the two panels. For binary files (images, PDFs), you need a dedicated file comparison tool.

Is my data private?

Yes. All comparison happens in your browser. No text is sent to any server. Safe for code, contracts, financial data, and confidential documents.