Diff Checker — Compare Text and Code Online
Compare text, files, and code (e.g. JS, JSON, XML) to find differences with HCODX Diff Checker online for free. Use our desktop app for private, offline diffs.
Visualize text & code changes clearly
A simple before/after — modifications stand out at a glance, just like a code review.
function calculateDiscount(price, percent) {
// Calculate the discount amount
const discount = price * (percent / 100);
// Return the final price
return price - discount;
}
const finalPrice = calculateDiscount(99.99, 15);
function calculateDiscount(price, percent, maxDiscount = Infinity) {
// Calculate the discount amount
let discount = price * (percent / 100);
// Apply maximum discount cap if provided
if (discount > maxDiscount) discount = maxDiscount;
return price - discount;
}
const finalPrice = calculateDiscount(99.99, 20, 25);
Built for engineers, writers & reviewers
Whether you're reviewing pull requests or comparing contract drafts, the workflow is the same.
Code review & versioning
Compare versions of your code to track changes, review pull requests, or understand what changed between commits.
Legal & contract review
Spot added, removed, or modified clauses between contract drafts to ensure compliance and accuracy.
Configuration management
Compare configuration files across environments to identify inconsistencies and verify deployments.
Content revision
Compare drafts of articles, documentation, or any text to review edits before publishing.
How our diff checker compares
A focused alternative to GitHub-style diffs — with deeper text-comparison modes and zero setup.
| Feature | HCODX Diff Checker | GitHub Diff | VS Code Diff | Other tools |
|---|---|---|---|---|
| Free to use | ✓ | ✓ | ✓ | ✓ |
| No installation needed | ✓ | ✓ | ✗ | ✓ |
| Multiple comparison levels | ✓ | ✗ | ✗ | ✗ |
| Syntax highlighting | ✓ | ✓ | ✓ | ✗ |
| Language-specific diffs (JSON, CSS) | ✓ | ✗ | ✗ | ✗ |
| Comprehensive statistics | ✓ | ✗ | ✗ | ✗ |
| File upload support | ✓ | ✓ | ✓ | ✓ |
| 100% client-side privacy | ✓ | ✗ | ✓ | ✗ |
How to compare text & code files
From paste to diff in under 30 seconds.
Paste your original content
Drop a file or paste your original text into the left editor. Pick a syntax for highlighting if you're working with code.
Add the modified version
Place the updated version in the right editor. Match the syntax to the content type for the cleanest highlighting.
Configure your options
Choose the comparison level — character, word, line, or specialized for CSS/JSON. Toggle whitespace or case sensitivity as needed.
Run the comparison
Click Find Differences. The diff is computed locally — usually instant, even for large files.
Review & export
Examine the highlighted result. Copy or download the diff for sharing in commits, reviews, or documentation.
Frequently asked questions
Everything you might wonder about how the comparison works.
Each mode offers a different granularity:
- Character — the most detailed view, highlighting each individual character that differs. Best for finding subtle typos or punctuation changes.
- Word — compares text as discrete words. The most useful mode for prose and most text documents.
- Line — compares content line by line. Best for source code where each line is a logical unit.
- Sentence — groups changes by complete sentences. Ideal for articles and documentation.
The CSS and JSON modes use syntax-aware algorithms to provide structurally meaningful comparisons rather than treating those formats as plain text.
The diff checker uses industry-standard algorithms — the same core comparison logic powering Git and other version control systems.
For best results with code:
- Use Line by line for most languages
- Enable syntax highlighting for clearer reading
- Use the language-specific CSS / JSON modes when applicable
- Toggle Ignore whitespace to focus on functional changes
For minified code, format it first with our JavaScript Beautifier for a cleaner diff.
Since the tool runs entirely in your browser:
- The practical limit is around 2 MB per file in most browsers
- Performance starts to degrade above ~500 KB
- Very complex diffs with thousands of changes may take longer to render
For files over 10 MB, a desktop tool like Beyond Compare or GNU diff will be more efficient. Your data is never uploaded — all processing happens locally for privacy.
No — this tool is designed for text-based files. It works with any text format: source code, markup, configuration files, plain text, etc. Binary files (images, PDFs, executables) cannot be meaningfully compared by text-based diff tools.
If a binary format has a text representation (such as Word documents), extract the text first and then compare it here.
Yes. Everything runs locally:
- Client-side processing — your text never leaves your browser
- No data storage — content is cleared when you close the tab
- No login required — use anonymously
- HTTPS only — secure transport for the page itself
This makes the tool suitable even for confidential content. As always, follow your organization's security policies for highly sensitive material.
- Side by side shows original and modified in parallel columns. Best for visual comparison and understanding context.
- Unified view combines both into a single column with + and − markers — similar to
git diffoutput. More compact and ideal for sharing.
The percentage reflects how much of the content stayed the same between the two versions. The tool tokenizes both inputs (into characters, words, or lines depending on the mode), measures how many tokens were unchanged versus added or removed, and reports the unchanged ratio as a percentage.
Different comparison modes can produce slightly different similarity values because each tokenizes content differently.
You can build similar functionality with open-source libraries:
- diff — the core JavaScript diff algorithms (character, word, line, etc.)
- diff2html — for visually rendering the differences
- CodeMirror — for editors with syntax highlighting
For server-side use, every major language has a counterpart (Python's difflib, Java's DiffUtils, etc.).
About text & code difference checking
Difference checking — or "diffing" — is the process of comparing two texts or code files to identify what has changed between them. Modern diff algorithms go beyond simple line-by-line comparison and can identify changes at multiple levels of granularity.
How diff algorithms work
At their core, diff algorithms find the longest common subsequence (LCS) between two texts and represent everything else as additions or deletions:
- Tokenization — break the input into comparable units (characters, words, lines)
- Matching — find the longest sequences appearing in both texts
- Differencing — identify what was added, removed, or changed
- Visualization — present the differences in a human-readable format
Applications of diff checking
- Version control — Git uses diffs to track every change to source code
- Code reviews — review only what changed instead of entire files
- Document revision — track edits in legal documents, contracts, articles
- Debugging — pinpoint what changed when a bug appeared
- Collaboration — merge contributions from multiple authors
- Compliance — verify approved changes match what was implemented
Best practices
- Choose the comparison level that matches your content (character / word / line)
- Enable syntax highlighting for code to make changes more visible
- Ignore whitespace when comparing code to focus on functional changes
- Use specialized modes (CSS, JSON) for structured data
- For very large files, focus on specific sections rather than the entire file
- Normalize formatting first when possible (use a beautifier)
Common diff formats
- Unified diff — changed regions with context, using + and − markers
- Side-by-side (split) diff — original and modified in parallel columns
- Word diff — highlights specific words that changed within lines
- Semantic diff — understands code structure to show meaningful changes