📄 Text Diff Checker
Compare two texts side by side. See additions, deletions, and changes highlighted.
Last updated: May 18, 2026 · By Λ
Free Text Diff Checker
Compare two blocks of text and instantly see the differences highlighted. Supports line-level and word-level diff with additions shown in green and deletions in red. Toggle options for ignoring whitespace or case. Perfect for comparing code, documents, or any text content. The comparison itself is computed by script on your own computer, and neither text box's contents ever travel over the network.
What is a Text Diff Checker?
A text diff checker compares two blocks of text and highlights the differences between them. The term "diff" comes from the Unix diff utility, which has been a foundational tool in software development since the 1970s. Diff tools identify which lines have been added, removed, or modified, making it easy to see exactly what changed between two versions of a document, configuration file, code snippet, or any other text content.
This free online diff checker uses the Myers diff algorithm, the same algorithm behind Git's diff output. It provides both line-level and word-level highlighting, so you can see not just which lines changed but exactly which words within those lines were modified. Options for ignoring whitespace differences and case sensitivity make it flexible enough for comparing code, prose, data files, and more. Because the algorithm executes inside the page you are viewing, both inputs stay private to your own session.
How to Use This Tool
- Paste the original text into the left text area and the modified text into the right text area. You can type directly or paste content from files, emails, or web pages.
- Click "Compare" to generate the diff. Additions appear highlighted in green, deletions in red, and unchanged lines in the default text color.
- Use the toggle options to customize the comparison: enable word-level highlighting for detailed inline changes, ignore whitespace to focus on meaningful content differences, or ignore case to treat uppercase and lowercase as equivalent.
- Use the "Swap" button to quickly reverse the original and modified texts, or "Clear" to reset both fields and start a new comparison.
Key Features
- Word-Level Highlighting - Goes beyond line-level diffs to highlight the specific words that changed within modified lines, making it easy to spot small edits in long lines.
- Myers Diff Algorithm - Uses the same proven algorithm as Git to produce minimal, accurate diffs that show the smallest set of changes needed to transform one text into the other.
- Whitespace Ignoring - Toggle this option to ignore differences in spacing, tabs, and trailing whitespace, which is especially useful when comparing code that may have been reformatted.
- Case-Insensitive Mode - Treat uppercase and lowercase letters as identical during comparison, helpful when case differences are not meaningful for your use case.
- Change Statistics - Displays a summary of additions, deletions, and unchanged lines along with the processing time, giving you a quick overview of how much changed.
Frequently Asked Questions
What types of text can I compare?
You can compare any plain text content: source code in any programming language, configuration files, CSV data, JSON or XML documents, written prose, legal contracts, or even raw log output. The tool treats the input as plain text and does not parse or interpret the content, so it works equally well with any format.
How large can the compared texts be?
There is no hard limit on text size. The Myers algorithm is efficient and handles thousands of lines in milliseconds. For very large files with tens of thousands of lines, performance depends on your device's processing power, but most modern browsers handle these sizes without noticeable delay.
What is the difference between line-level and word-level diff?
Line-level diff marks entire lines as added, removed, or unchanged. This is useful for a quick overview but can be hard to read when only a small part of a long line changed. Word-level diff goes further by highlighting the specific words within a changed line that differ, making it much easier to identify exactly what was edited. You can toggle word-level highlighting on or off depending on your preference.
Is my text data stored or logged anywhere?
No. The diff comparison runs entirely in your browser using client-side JavaScript. Your text is never sent to any server, stored in any database, or included in analytics. This makes the tool safe for comparing confidential documents, proprietary code, or any sensitive content.