Text Tools

Text Diff Checker

Compare two texts side by side and see additions, deletions, and unchanged content highlighted. Word-level diff with change statistics.

Quick Answer

Paste your original text on the left and the modified version on the right. The tool highlights additions in green, deletions in red, and leaves unchanged text in gray. Works for any text including code, documents, and articles.

+8
Words Added
-10
Words Removed
12
Words Unchanged
18
Total Changes

Diff Output

The quick brownred fox jumpsleaps over the lazy dog.cat. This is the second line. AndA anew thirdfourth line that stays thewas same.added.

About This Tool

The Text Diff Checker compares two blocks of text and highlights every difference at the word level. Additions appear in green, deletions in red, and unchanged text in gray. This tool is useful for proofreading edits, comparing document versions, checking code changes, or verifying contract modifications.

Word-Level vs. Line-Level Diffing

This tool uses word-level diffing, which breaks text into individual words and whitespace tokens, then finds the longest common subsequence between the two versions. This approach shows exactly which words changed within a line, rather than just flagging entire lines as different. For very large texts, the tool automatically falls back to line-level comparison for performance.

Common Use Cases

Writers use diff checkers to review editorial changes and ensure no unintended modifications were made. Developers compare configuration files or documentation versions. Legal professionals verify that contract revisions match agreed-upon changes. Students compare draft versions of essays. The tool works for any plain text content.

Privacy and Security

All comparison happens entirely in your browser. No text is ever sent to a server or stored anywhere. This makes the tool safe for comparing sensitive documents, legal contracts, medical records, or any confidential content. The tool continues to work even if you go offline after the initial page load.

Frequently Asked Questions

How does the text diff checker work?
The tool splits both texts into words and uses a Longest Common Subsequence (LCS) algorithm to find the optimal alignment between them. Words present in only the original text are marked as deletions (red), words in only the new text are additions (green), and matching words are unchanged (gray). This word-level approach gives more granular results than line-level diffing.
Can I compare code with this tool?
Yes, this tool works for any plain text including code. However, for code-specific diffing with syntax awareness, a dedicated code diff tool or IDE's built-in diff viewer may be more appropriate. This tool treats all text equally and does word-level comparison, which works well for prose, documentation, and simple code changes.
Is there a size limit for comparison?
The tool handles texts up to several thousand words efficiently in your browser. For very large texts (over 5,000 words each), it automatically switches to a simpler line-level diff for performance. All processing happens locally in your browser with no server communication.
What do the colors mean?
Green background indicates text that was added (present in the new text but not the original). Red background indicates text that was removed (present in the original but not the new text). Gray/unchanged text appears in both versions. This follows the universal convention used by tools like Git and code review platforms.
Is my text private?
Yes, completely. The diff comparison runs entirely in your browser using JavaScript. Your text is never sent to any server, stored, or logged. The tool works offline once loaded. This makes it safe for comparing sensitive documents, contracts, or confidential content.

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