Skip to main content
Article Formatter

Text Diff Checker

Paste two versions of text below to see exactly what changed between them.

0
Added
0
Removed
0
Unchanged
0
Total Lines

Options

Paste original text
Paste modified text

Paste text into both fields and click "Compare" to see the differences.

What Is a Text Diff Checker?

A diff checker compares two pieces of text and shows you exactly what changed between them. It highlights which lines were added, which were removed, and which stayed the same. If you've ever used "Track Changes" in Word or reviewed a pull request on GitHub, you've seen a diff before. This tool brings that same capability to any text, right in your browser.

The name "diff" comes from the Unix command that's been around since the 1970s. It works by finding the longest common subsequence between two texts - basically the largest set of lines that appear in both versions in the same order. Everything else is either an addition or a deletion.

When You'd Use This

Comparing document versions: You sent a contract to a client, they sent it back with "a few changes," and now you need to find exactly what they modified. Paste the original and their version, and every change lights up instantly. No more reading both versions side by side hoping you catch everything.

Reviewing content edits: An editor returned your blog post with revisions. Instead of accepting changes blindly, paste both versions here to see every modification. You'll catch rephrased sentences, deleted paragraphs, and subtle word swaps that might change your meaning.

Debugging code or config files: Something broke after a config change, and you're not sure what's different. Paste the working version and the current version to spot the difference immediately. It's faster than eyeballing two nearly-identical files.

Checking data exports: You exported a dataset yesterday and again today. Are they identical? The diff will tell you in seconds, showing any rows that were added, removed, or modified.

How the Options Work

Ignore case: Treats "Hello" and "hello" as the same line. Useful when comparing text where capitalization isn't meaningful, like email addresses or configuration values that are case-insensitive.

Ignore whitespace: Strips leading and trailing spaces and tabs before comparing. Turn this on when comparing code that might have been reformatted, or text that picked up extra spaces during copy-paste.

Ignore blank lines: Skips empty lines entirely during the comparison. Helpful when one version has extra spacing between paragraphs and you only care about the actual content differences.

Privacy First

Like every tool on Article Formatter, this diff checker runs 100% in your browser. The text you paste never leaves your computer - there's no server processing, no uploads, and no data storage. Close the tab and your text is gone. That makes it safe for comparing contracts, internal documents, credentials files, or anything else you wouldn't want on someone else's server.

Want to learn more about text comparison techniques? Read our in-depth guide on how to compare two texts and find differences, covering command-line diff, Python, JavaScript, Git, and more.

Need to work with your text in other ways? Use the Article Formatter to clean up encoding issues, the Word Counter to analyze your content, or the Remove Duplicate Lines tool to deduplicate lists. For format conversion, check out Markdown to HTML and CSV to Table Converter.

Frequently Asked Questions

How does the diff algorithm work?
This tool uses the Myers diff algorithm, the same approach used by Git and most professional diff tools. It finds the longest common subsequence between your two texts - the largest set of lines that appear in both versions in the same order - then marks everything else as either an addition or a deletion. For very large texts over 10,000 lines, it switches to a faster line-matching algorithm.
Is my text sent to a server when I compare?
No. The entire comparison runs locally in your browser using JavaScript. Your text never leaves your computer - there are no server requests, no uploads, and nothing is stored. Close the tab and the data is gone. This makes it safe for comparing contracts, credentials, internal documents, or any sensitive content.
What do the Ignore Case and Ignore Whitespace options do?
Ignore Case treats uppercase and lowercase letters as identical, so "Hello" and "hello" are considered the same line. Ignore Whitespace strips leading and trailing spaces and tabs before comparing, which is useful when text has been reformatted or picked up extra spaces during copy-paste. You can combine both options.
Can I compare code or configuration files with this tool?
Yes. The diff checker works with any plain text, including source code, JSON, XML, YAML, CSV, config files, SQL, and log files. It preserves whitespace and shows line numbers, so you can pinpoint exactly where a config change or code edit happened. For code with indentation changes, turn on Ignore Whitespace to focus on actual content differences.
Is there a size limit on the text I can compare?
There is no hard limit since everything runs in your browser. The Myers algorithm handles texts up to about 10,000 lines efficiently. Beyond that, the tool automatically switches to a faster comparison method that still produces accurate results. For typical documents, articles, config files, and code files, performance is essentially instant.