Text Diff Comparison (Diff Checker)

What is Diff Checker?

Diff Checker is a tool for comparing two texts and identifying differences. When you paste the before and after versions of a document, program source code, configuration files, portions of CSV files, email drafts, and more into the left and right input fields, it displays added, deleted, and unchanged lines in different colors.This makes it easier to spot even single-character changes that are easy to overlook with a visual inspection alone.

This tool first calculates the overall differences on a line-by-line basis. If deleted and added lines are adjacent, it also highlights the character-level differences as corresponding changes. This allows you to quickly identify rephrased text, numerical changes, variable name corrections, added spaces, and more.You can choose to ignore whitespace and case differences as needed, allowing you to perform comparisons tailored to your specific needs.

Comparisons are performed entirely within the user’s browser using JavaScript. Text or code entered is not sent to the server for comparison. However, please verify the security of environments outside of this tool—such as the clipboard history on shared devices or browser extensions—yourself.

How to Use

1. Paste the original text on the left and the revised text on the right.
2. Select options as needed to ignore spaces and case, or to display only differences.
3. When you click "Compare Differences," the page will automatically scroll to the location of the comparison results.
4. Green lines indicate additions, red lines indicate deletions, and white lines indicate no changes.
5. To save your changes, use "Copy Differences."

How to Interpret Comparison Results

• The two columns on the far left show the row numbers for the source and destination, respectively.
• Lines marked with a red minus sign indicate content that has been removed from the source.
• The green lines with the plus sign indicate items that have been added to the comparison list.
• The bold text within a line indicates the characters that have actually changed in that line.

Precautions for Use

• Very large files use a lot of browser memory, so please split them into smaller sections as needed for comparison.
• When "Ignore spaces" is enabled, consecutive spaces, tabs, and leading and trailing spaces within a line are treated as equivalent for comparison purposes.
• This tool is designed for comparing text. It cannot compare formatting, images, or comment histories in Word or PDF files.

Frequently Asked Questions

What is Diff Checker?

This tool compares two texts and visualizes the additions, deletions, and changes.

Will the entered data be sent to the server?

No. The difference calculation is performed by JavaScript within the browser.

Can we compare the source code as well?

Yes. You can compare content that can be pasted as text, such as PHP, JavaScript, HTML, CSS, SQL, and configuration files.

Can you tell the difference in the number of characters?

Yes. In areas where deleted and added lines appear consecutively, highlight the different text in a darker color.

Can you ignore differences in spaces and tabs?

If you select "Ignore whitespace differences," the system will normalize and compare the text by removing consecutive spaces, tabs, and other whitespace characters.

Can uppercase and lowercase letters be treated as the same when comparing them?

Yes. Please select "Ignore case."

Can I display only the lines that have changed?

Yes. If you select “Show only changed rows,” you can hide rows that haven’t been modified.

Can I switch the left and right sides for comparison?

Yes. Clicking "Swap Left and Right" will swap the two entries.

Can I copy the comparison results?

Yes. You can copy them using a format where a plus sign is added to the rows to be added and a minus sign to the rows to be deleted.

Can I compare Word and PDF files directly?

Direct file comparison is not supported. Please extract the text you want to compare and paste it into the input field.

Can you compare large amounts of text?

You can compare items up to a certain quantity, but to prevent overloading the system, there is a limit on extremely large combinations. Please divide the range into smaller groups for comparison.