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CollateKit

Text Diff Checker

Paste or type two versions of a text below, then click Compare to see what changed. Added lines are highlighted, removed lines are marked, and a summary shows the total changes.

Free Forever
Works Completely In Your Browser
No Upload Required
Privacy Friendly
Click "Compare" to see differences…

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About this tool

The Text Diff Checker compares two blocks of text line by line and highlights exactly what changed. Paste your original text into the left panel and the updated version into the right panel, then click Compare. Lines that appear only in the modified version are marked with a + and highlighted in blue. Lines that were removed are marked with a - and highlighted in red. Lines that are the same in both versions appear in grey without a prefix.

A summary bar appears after each comparison showing the count of Added lines, Removed lines and the total Changes. You can copy the full diff result to your clipboard with the Copy button, which includes the +, -, and space prefixes so it is ready to paste into a document or a code review comment.

Three comparison options give you control over what counts as a difference. Ignore Case treats uppercase and lowercase letters as equal. Ignore Whitespace collapses extra spaces and tabs before comparing, so a line that only differs in spacing is treated as unchanged. Ignore Empty Lines skips blank lines on both sides, which is useful when one version has extra line breaks. Developers use these options when comparing config files or code where formatting varies but the content is the same. Writers and editors use the default settings to catch every change including punctuation and spacing. When you are comparing JSON files, format both versions with the JSON Formatter & Validator first so indentation differences do not hide real content changes. If the text includes CSS color values, convert them to the same format with our Color Picker & Converter before comparing.

The comparison uses a Longest Common Subsequence (LCS) algorithm, the same approach used by version control tools like Git. Everything runs in your browser — your text is never sent to a server or stored anywhere. The tool supports up to 5,000 lines per side.

How to use

  1. 1Paste the original text into the Original panel and the updated text into the Modified panel. Or click Load Sample to try an example.
  2. 2Optionally enable Ignore Case, Ignore Whitespace, or Ignore Empty Lines to control what counts as a difference.
  3. 3Click Compare. Added lines are shown in blue (+), removed lines in red (-), and unchanged lines in grey.
  4. 4Check the summary bar for the count of Added, Removed and total Changes. Click Copy to copy the diff result to your clipboard.
  5. 5Click Clear to reset both panels and start a new comparison.

Example

Two versions of a short config file. The second version adds a new field and changes the version number.

Original
name: my-app
version: 1.0.0
debug: false
Modified
name: my-app
version: 1.1.0
debug: false
log_level: info
Diff result
  name: my-app
- version: 1.0.0+ version: 1.1.0  debug: false
+ log_level: info

Common uses

  • Comparing document drafts to see what an editor added or removed
  • Reviewing configuration or code changes before applying them
  • Checking two lists (email addresses, IDs, keywords) for additions and removals
  • Verifying that copied or pasted content matches the original exactly

Frequently asked questions

What is a text diff checker?
A text diff checker compares two versions of a text and shows exactly what changed between them: which lines were added, which were removed and which stayed the same. Developers use it to review code and config changes, writers use it to compare drafts, and anyone can use it to spot differences without reading both versions line by line.
What is comparing text?
Comparing text means checking two pieces of text against each other to find where they match and where they differ. Instead of reading both versions yourself, a comparison highlights the additions, deletions and unchanged parts so you can see the differences at a glance. It is useful for edited documents, contracts, configuration files, code and copied content.
How does the diff checker work?
Paste the original text into one box and the changed text into the other. The tool compares the two line by line, finds the lines they have in common, and marks the remaining lines as added or removed. The result is shown side by side so you can see every change. The comparison runs in your browser, so your text is not uploaded anywhere.
Does a diff checker compare strings and lists?
Yes. Text is compared line by line, so a list works best when you put one item on each line, such as email addresses, keywords, file names or IDs. The tool then shows which items were added, removed or unchanged. A short string can be compared too: put each version in its own box. Because the comparison is line based, order matters, so sort both lists first if you only care about their contents.

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