Compare Two Texts and Find the Differences
The Cluster Tools Text Diff Checker shows you exactly what changed between two versions of a text — line by line and character by character. Additions are highlighted in green, deletions in red, unchanged sections in neutral. There's no guessing involved.
This runs entirely in JavaScript in your browser using the Myers diff algorithm. Your text — which might contain confidential contracts, source code with credentials, or proprietary content — is never sent to a server.
The Myers Diff Algorithm
Cluster Tools uses the Myers diff algorithm (Eugene Myers, 1986), the same algorithm used by Git for showing file changes. It finds the shortest edit script — the minimum number of line insertions and deletions needed to transform text A into text B. This gives intuitive, meaningful diffs rather than arbitrary change representations.
When to Use a Text Diff Tool
Reviewing document revisions — a client returns a contract with "some small changes." Instead of reading every line, paste both versions and see exactly what changed.
Comparing code snippets — checking the difference between two versions of a function, a configuration file, or a SQL query.
Verifying copy changes — comparing the original and final versions of web page copy, email campaigns, or blog posts before publishing.
Catching plagiarism or unauthorized changes — comparing a submitted document against an original to identify differences.
Translation verification — comparing translated content against the source to identify passages that may have been added or omitted.
View Modes
Side-by-side — the two texts are shown in parallel columns, with differences highlighted. Best for understanding context around changes.
Inline — changes are shown in a single column, with additions and deletions interleaved. Compact and efficient for dense comparisons.
Character-level diff — within changed lines, highlights exactly which characters differ (not just which lines). Critical for catching single-character typos, punctuation changes, or number substitutions.
Step-by-Step: How to Compare
- Paste your original text into the left panel.
- Paste the revised text into the right panel.
- The differences are highlighted automatically as you type.
- Use the diff mode selector to switch between side-by-side and inline views.
Frequently Asked Questions
Does it compare by line or by character? By default, it diffs by line and then performs character-level diffing within changed lines. The character-level view is shown on request.
Can it compare code? Yes — it treats code as plain text and diffs it accordingly. It doesn't understand programming language syntax; for semantic code diffs, you'd need language-aware tools.
What about whitespace differences? By default, whitespace changes (extra spaces, tabs, trailing spaces) are shown as changes. You can enable "ignore whitespace" mode to hide these and focus on substantive content differences.
What's the maximum text length? No hard limit. The Myers algorithm is O(ND) where N is the number of elements and D is the edit distance. Very large texts with many differences may be slower to compute but will complete correctly.
Related Tools
- Word Counter — count words in each version before comparing.
- Remove Duplicate Lines — clean up text before diffing.
- JSON Formatter — format JSON from both versions before comparing them.
- Case Converter — normalize capitalization before comparing.