ToolzyLab
Compare two code snippets or files side by side with color highlights, synced scrolling, optional whitespace-insensitive comparison, and detailed change reporting. Perfect for JavaScript, HTML, CSS, JSON, XML, config files, logs, and plain text.
Paste your old and new code into the editors or upload two files. The tool compares them line by line, highlights additions, removals, and changed sections, and gives you a clean report with counts and quick export options.
Drop or select the original / old / source code file.
📄 old code · source versionDrop or select the updated / new / target code file.
📄 new code · updated versionPaste old code on the left and updated code on the right, then run the diff.
Compare both versions line by line. Added, removed, and changed lines are color coded.
Quick report of important changed rows and text snippets.
Fast controls for power users.
Turn on Ignore whitespace when only spaces, tabs, or indentation changed. Turn on Ignore case when casing changes should not count as real diff noise.
A diff makes additions, deletions, and changed lines visible, but it cannot decide whether the new behavior is correct. Load or paste both versions, choose syntax highlighting, context, whitespace and case handling, wrapping, line numbers, and synchronized scrolling, then review the report alongside tests and version history.
Additions and deletions reverse meaning when inputs are swapped. Label or remember the baseline, then compare. Syntax highlighting improves scanning but does not parse program semantics. A line shown as removed and added may be a small edit, an indentation change, or a moved block depending on the selected view.
Whitespace can be cosmetic in some files and meaningful in Python, YAML, Makefiles, templates, regular expressions, and string literals. Case can change identifiers, paths, values, and commands. Start with an exact comparison, then suppress a category only to answer a specific review question.
A concise context view is useful for a report, while full side-by-side text helps understand surrounding control flow. Search for security-sensitive names, configuration keys, API endpoints, and removed validation. Run formatters, linters, tests, and version-control review before approving production changes.
Treat the diff as evidence of textual change and pair it with behavior checks.
The left side is normally the baseline and the right side the changed version. Confirm that orientation before reading additions and deletions, or use Swap when the inputs are reversed.
Only for a focused review where whitespace cannot affect meaning. Keep exact comparison for Python, YAML, indentation-sensitive templates, Makefiles, and strings.
A text diff typically matches lines rather than understanding refactoring intent. A moved block may therefore appear once as removal and again as addition, especially when nearby text also changed.
No. It shows text differences, not runtime behavior, side effects, types, security, or compatibility. Use tests and language-specific analysis.
Context is the number of unchanged lines shown around each change. More context helps explain control flow; less context creates a shorter review report.
Yes, but line-ending normalization can create noise or hide a repository-wide change. Check the project's expected LF or CRLF policy before ignoring it.