Diff Patch Generator
Compare original and updated text, then generate a lightweight line diff patch.
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Original
Updated
Patch Output
About Diff Patch Generator
This diff patch generator compares two versions of text and produces a unified diff format patch, showing exactly what lines were added, removed, or unchanged. It's useful for code reviews, sharing fixes, documenting changes, and submitting patches to projects.
What Is a Diff Patch?
A diff patch is a standardized way to represent changes between two files. The unified diff format (which this tool produces) uses simple prefixes to indicate change types:
--- original +++ updated line 1 (unchanged - prefixed with space) -line 2 (removed) +line 2 modified line 3 (unchanged)
Diff Output Format
| Prefix | Meaning | Example |
|---|---|---|
(space) |
Unchanged context line | function hello() { |
- |
Line removed from original | - console.log("old"); |
+ |
Line added in updated version | + console.log("new"); |
--- |
Original file header | --- original |
+++ |
Updated file header | +++ updated |
Example Diff
Original code:
function greet(name) {
return "Hello, " + name;
}
Updated code:
function greet(name) {
if (!name) {
name = "World";
}
return `Hello, ${name}!`;
}
Generated patch:
--- original
+++ updated
function greet(name) {
+ if (!name) {
+ name = "World";
+ }
- return "Hello, " + name;
+ return `Hello, ${name}!`;
}
Common Use Cases
- Code Reviews: Show exactly what changed between versions for team review
- Bug Fixes: Create patches to share fixes without sending entire files
- Open Source Contributions: Submit patches to projects that accept diff submissions
- Configuration Changes: Document changes to config files for audit trails
- Documentation Updates: Track changes in documentation or translation files
- Merge Conflict Resolution: Generate patches to manually apply changes after merges
How to Apply Patches
- Unix/Linux:
patch original_file < patchfile.diff - Git:
git apply patchfile.difforgit am patchfile.diff - Windows (Git Bash): Same as Unix commands above
- Manual: Use the diff output as a guide to manually edit the file
How to Generate a Diff Patch
- Paste original text: Copy the original version of your text/code into the left "Original" box.
- Paste updated text: Copy the modified version into the right "Updated" box.
- Click Generate Patch: The tool will compare both versions and generate a unified diff.
- Review the diff: Lines with '-' were removed, lines with '+' were added, lines with space are unchanged.
- Copy the patch: Click "Copy Patch" to copy the diff output for sharing or applying.
Tips for Best Results
- Ensure both versions have the same general structure for meaningful diffs
- Small, focused changes produce clearer patches than large wholesale rewrites
- For code, consider formatting both versions before comparing
Frequently Asked Questions
- What is a diff patch and how does it work?
- A diff patch is a file that shows the differences between two versions of text or code. It uses a standard format where lines starting with '-' are removed, lines starting with '+' are added, and lines starting with ' ' (space) are unchanged context. This format is widely used in version control (Git), code reviews, and software patches.
- What is the difference between unified diff and context diff?
- Unified diff (the format this tool produces) shows removed lines with '-' prefix and added lines with '+' prefix in a single compact block. Context diff uses '---' for removed and '+++' for added lines with more context. Unified diff is the modern standard used by Git and most development tools.
- How do I apply a generated patch file?
- Use the 'patch' command in Unix/Linux: 'patch original_file < patchfile.diff'. In Git, use 'git apply patchfile.diff' or 'git am' for email patches. Windows users can use tools like TortoiseGit or the Git Bash terminal.
- What are common use cases for diff patches?
- Common uses include: code review submissions, sharing bug fixes, documenting configuration changes, creating hotfixes, submitting patches to open source projects, and tracking changes in text files like documentation or translation files.
- Can this tool compare entire files or just text snippets?
- This tool works with any text content - you can paste entire files or just code snippets. For very large files (thousands of lines), consider using dedicated diff tools like 'diff' command, Git diff, or specialized comparison software.
- Why are some unchanged lines shown in the diff?
- These are context lines (prefixed with space) that help orient readers and ensure the patch can be applied correctly. They provide surrounding context so the patch tool knows exactly where to apply changes.