Free Diff Checker Online
Compare two blocks of text side by side and instantly see every addition, deletion, and change — highlighted line by line.
How it works
Paste original text
Put the original version in the left panel.
Paste modified text
Put the changed version in the right panel.
Compare
Click Compare or press Ctrl+Enter. Differences are highlighted line by line.
Review changes
Green lines are additions, red lines are deletions. Unchanged lines are shown for context.
Common use cases
Code review spot-checks
Paste two versions of a function or config file to see exactly what changed before approving a PR.
Document version comparison
Compare two versions of a contract, report, or specification to identify every change between drafts.
Config file auditing
Compare server configs, environment files, or Kubernetes manifests to spot unintended differences between environments.
API response comparison
Paste two JSON API responses to find what changed between releases or between two environments.
Frequently asked questions
What algorithm does this use?
The diff uses a Myers diff algorithm — the same algorithm git uses. It computes the minimum number of insertions and deletions to transform one text into the other.
Is this a line-by-line or character-by-character diff?
Line-by-line diff with color highlighting. Each line is categorized as unchanged, added, or removed.
Can I compare code files?
Yes — paste any text content including source code, JSON, YAML, configuration files, or plain text. The diff does not need to understand the file format.
Does my content get uploaded?
No. The diff algorithm runs entirely in your browser using JavaScript. Your text never leaves your tab.
What do the colors mean?
Green background = lines added in the new version. Red background = lines removed from the original. White/grey = unchanged lines shown for context.
How large a diff can this handle?
The browser-based diff handles up to several thousand lines efficiently. Very large files (100K+ lines) may be slow — split them first for best performance.