Text Diff Checker
Compare two texts side-by-side and highlight the differences between them.
What Is a Text Diff Checker?
A Text Diff Checker is a tool that compares two versions of a text and highlights every addition, deletion, and unchanged section. It's the same technology used by version control systems like Git to track changes in source code, documents, or any plain text.
This tool uses a Longest Common Subsequence (LCS) algorithm to produce accurate, line-by-line and word-level comparisons, giving you both side-by-side and unified diff views instantly in your browser — no upload required.
How to Use the Text Diff Checker
- Step 1: Paste your original text into the left textarea.
- Step 2: Paste the modified (new) version into the right textarea.
- Step 3: Use the options to ignore case, extra whitespace, or blank lines if needed.
- Step 4: Click Compare to generate the diff.
- Step 5: Switch between Side by Side, Unified, and Word Diff views.
- Step 6: Use Copy Diff to export the results as plain text.
Common Use Cases
- Comparing two versions of a document or essay
- Reviewing code changes without a full IDE
- Checking what changed between two configuration files
- Proofreading edited content against the original draft
- Verifying translation accuracy line by line
- Spotting unintended changes in copied/pasted content
Frequently Asked Questions
Is my text stored or sent to a server?
No. All comparisons happen entirely in your browser using JavaScript. Your text never leaves your device and is not stored anywhere.
What is the difference between Side by Side and Unified view?
Side by Side shows the original and modified texts in two parallel columns, making it easy to visually scan both at once. Unified view interleaves all lines into a single column, with removed lines marked in red (−) and added lines in green (+), similar to a standard Git diff output.
What does Word Diff mode do?
Word Diff mode goes beyond line-level comparison and highlights the exact words that changed within each line. This is useful when only a few words differ on a line that would otherwise appear as a full removal and addition.
How large can the texts be?
Since everything runs in-browser, very large texts (tens of thousands of lines) may cause a short processing delay. For most practical documents and code files, the comparison is nearly instant.
What do the Ignore options do?
Ignore Case treats uppercase and lowercase letters as equal. Ignore Extra Whitespace normalises multiple spaces/tabs on a line before comparing. Ignore Blank Lines skips lines that contain only whitespace when computing the diff.
Can I compare code files with this tool?
Absolutely. The diff checker works on any plain text, including source code, JSON, XML, CSV, Markdown, and more. Simply paste the file contents into the two text areas.