Text Diff Checker
Compare two texts and see additions, deletions and changes highlighted. Import files, export reports. All processing happens in your browser.
100% local – nothing uploadedOriginal Text
Modified Text
What is Text Diff Checker?
Text Diff Checker is a free online tool that compares two pieces of text and highlights the differences. It supports character-level, word-level and line-level comparison. All processing happens entirely in your browser – no text is ever uploaded to any server.
How to Use
- Paste or type the original text in the left area and the modified text in the right area.
- Optionally import text files by clicking Import or dragging files into the input areas.
- Choose a comparison mode: Auto, By Line, By Word, or By Character.
- Adjust comparison options such as ignore case or ignore whitespace if needed.
- Click Compare to see the differences highlighted in the results below.
- Use the navigation buttons to jump between differences, or export the report as HTML, TXT or Patch.
Character, Word and Line Comparison
Character comparison checks every single character and is best for short texts or finding subtle changes. Word comparison splits text by words and is ideal for articles, contracts and general prose. Line comparison works line by line and is perfect for code, configuration files, logs and structured text. The Auto mode selects the most suitable method based on text length and structure.
Side-by-Side vs Unified View
Side-by-side view shows the original text on the left and the modified text on the right, aligned for easy comparison. Unified view combines both texts into a single list where deletions appear with a minus sign and additions with a plus sign, similar to the format used by Git and other version control systems.
Ignore Options
You can choose to ignore case differences, whitespace changes, blank lines, punctuation and numbers. When ignore options are enabled, the comparison uses normalized text internally but displays the original text, so your input is never permanently modified. If no differences are shown after enabling ignore options, it means the texts only differ in the aspects you chose to ignore.
Supported File Formats
You can import any plain text file including TXT, MD, CSV, TSV, JSON, XML, HTML, CSS, JavaScript, TypeScript, LOG, YAML, SQL and other text-based formats. Files are read using the browser File API and never uploaded. The maximum recommended file size is 10 MB.
Common Use Cases
This tool is useful for comparing article revisions, reviewing contract changes, checking code and configuration differences, verifying translation updates, analyzing log changes, inspecting copied content for modifications, comparing Markdown or JSON files, and reviewing any text before and after editing.
Diff Algorithm
This tool uses the well-known Myers diff algorithm through the jsdiff library. It computes the longest common subsequence to find the minimum number of changes between two texts. The algorithm is efficient for most texts up to several hundred kilobytes. For very large texts, line comparison mode is recommended.
Data & Privacy
All text comparison is performed entirely in your browser. No text content, file names or comparison results are sent to any server. No data is stored in localStorage or cookies. When you close this page, all temporary data is immediately released. No analytics tracking includes your text content.
Limitations
Very large files over 1 MB may cause browser slowdowns. Character-level comparison is not recommended for texts longer than a few thousand characters. Binary files cannot be compared. The tool does not support comparing more than two texts simultaneously. For extremely large files, consider using dedicated command-line diff tools.
Frequently Asked Questions
Is my text uploaded to a server?
No. All text processing happens entirely in your browser. Nothing is uploaded to any server.
What is the difference between character, word and line comparison?
Character comparison checks every single character. Word comparison splits text by words. Line comparison works line by line. Choose based on your text type and what level of detail you need.
How do I ignore case differences?
Enable the Ignore case checkbox in the comparison options. The comparison will treat uppercase and lowercase letters as identical.
How do I ignore whitespace and blank lines?
Enable Ignore whitespace to treat consecutive spaces as one. Enable Ignore blank lines to skip empty lines during comparison.
What text file formats are supported?
You can import TXT, MD, CSV, TSV, JSON, XML, HTML, CSS, JS, TS, LOG, YAML, SQL and other plain text files up to 10 MB.
Can I compare code?
Yes. Line comparison mode is ideal for code. You can import code files directly and see changes highlighted line by line with inline word-level differences.
Does it support Chinese, Japanese and Korean text?
Yes. The tool uses Intl.Segmenter for proper word segmentation in CJK languages when available in the browser.
Why does it show no differences after enabling ignore options?
This means the texts only differ in aspects you chose to ignore, such as case, whitespace or blank lines. The original content is preserved and not modified.
How do I export comparison results?
You can export as a self-contained HTML report, a plain text report, or a Unified Diff patch file. You can also copy specific additions, deletions or the unified diff to clipboard.
How large can the files be?
The recommended maximum is 10 MB per file. Texts under 100 KB are compared in real time. Larger texts may use debouncing or require manual comparison.
Does the HTML report contain the original text?
Yes. The exported HTML report is self-contained and includes all diff results with inline CSS styling. It can be opened in any browser without internet access.
Can I use this on my phone?
Yes. The tool is fully responsive and works on mobile browsers. Input areas stack vertically on small screens and the unified view is recommended for mobile.