Compare code in Original and Modified
Use Original and Modified for a normal two-version comparison. The tool also renders when only one panel contains text, comparing that content with an empty side. Changes trigger a short delayed re-render while you type.
- Paste or load content in either panel. Use Upload or Drop file to load a file.
- Choose a language from Language, or leave Auto-detect selected. Auto-detect checks Modified first and uses Original only when Modified is empty.
- Select Side-by-side or Unified, then review the rendered comparison.
Use the comparison controls
- Choose Side-by-side to show Original and Modified columns with synchronized scrolling, or Unified to combine changes and context in one stream.
- Ignore leading/trailing whitespace excludes leading and trailing spacing from line equality checks.
- Ignore whitespace differences replaces each run of spaces or tabs with one space and trims the result before comparison. The displayed source text remains unchanged.
- Show whitespace as visible spaces displays entered spacing more explicitly. It does not add whitespace markers or replace spaces and tabs with symbols.
Read the diff results
The comparison is line-based and uses a Myers diff. Results include syntax highlighting, line numbers, and Similarity, Added, Removed, and Unchanged statistics. Long unchanged runs can be collapsed into clickable summaries; the grouping uses fixed line context, not syntax-aware code analysis.
Copy a unified patch
After either input contains text, the Unified patch section is displayed. It contains unified-style text with fixed a/original and b/modified headers. Select Copy patch to copy it. If the inputs produce no diff operations, such as identical inputs, the textarea is empty. The implementation does not validate the text with git apply.
Limits and privacy scope
- Comparison, syntax highlighting, and patch generation run in client-side JavaScript. The inspected tool script does not send entered code to a server.
- Statistics are based on line operations, and the whitespace options change the comparison keys.
- No explicit maximum file size, supported encoding list, or browser compatibility limit is documented in the inspected implementation.
- The inspected implementation has no documented user-facing fallback if copying to the clipboard fails.
Frequently Asked Questions
How does the code diff checker detect the language?
With Auto-detect selected, the tool checks Modified first and uses Original only when Modified is empty. It analyzes code patterns for syntax highlighting. You can also choose a language manually. If no supported pattern is detected, it falls back to Plain text.
How does the tool compare code?
It performs a line-based Myers diff. The shared code viewer adds syntax highlighting, and long unchanged line runs can be collapsed into clickable summaries using fixed line context rather than syntax-aware analysis.
How do the whitespace controls work?
Ignore leading/trailing whitespace and Ignore whitespace differences change which lines are considered equal. Ignore whitespace differences replaces each run of spaces or tabs with one space and trims the result before comparison. Show whitespace as visible spaces preserves and displays the entered spacing more explicitly; it does not add whitespace markers.
Is the patch output compatible with git apply?
The tool creates copyable unified-style text with fixed a/original and b/modified headers. It does not validate that the result can be applied with git apply, and identical inputs produce an empty patch textarea.
Is this tool private?
Comparison, syntax highlighting, and patch generation run in client-side JavaScript. The inspected tool script does not send entered code to a server, but the page does not establish broader storage or security guarantees.