AI Code Compare & Diff Tool (Free)
AI-powered code comparison for Python, JavaScript, Java, C++, and 100+ languages. Compare code versions, detect semantic differences, analyze logic changes, identify breaking changes. Understand what changed and why.
Paste code in both editors to see differences
Hint: Paste original code on left, modified code on right, then click Compare to see differences highlighted.
Hint: Paste your code, customize font size and line numbers, then click Export PDF to download formatted code.
Hint: Paste your JWT token to decode and view its header, payload, and signature. The tool validates token structure and format.
Hint: Select conversion type, paste your data, and get instant conversion. Supports JSON, YAML, XML, Excel, PDF, and more.
How It Works
- 1
Paste Original Code Version
Copy the original, previous, or baseline version of your code. Supports functions, classes, modules, or entire files from any programming language including Python, JavaScript, Java, C++, and 100+ others.
- 2
Paste Modified Code Version
Copy the updated, refactored, or alternative version. Can be the same language (version comparison) or different language (cross-language semantic comparison for migrations).
- 3
Receive AI Analysis
Get comprehensive comparison: semantic differences, logic changes, performance impact, breaking vs non-breaking changes, security implications, refactoring detection, and explanation of why changes matter.
Traditional Diff vs AI Analysis
| Feature | Traditional Diff | AI Code Compare |
|---|---|---|
| Analysis Type | Line-by-line text diff | Semantic code analysis |
| Understanding | Shows what changed | Explains why and impact |
| Formatting | Noise from whitespace | Ignores cosmetic changes |
| Refactoring | Shows everything different | Detects same logic |
| Cross-Language | Not supported | Compares across languages |
| Insights | None | Performance, security, breaking changes |
Examples
Example 1: Detecting Refactoring vs Logic Changes
def calculate_total(items):
total = 0
for item in items:
total += item['price'] * item['quantity']
tax = total * 0.08
shipping = 10 if total < 50 else 0
return total + tax + shippingdef calculate_order_total(order_items: list[dict]) -> float:
"""
Calculate total order cost including tax and shipping.
Args:
order_items: List of items with 'price' and 'quantity'
Returns:
Total cost with tax and shipping
"""
TAX_RATE = 0.08
FREE_SHIPPING_THRESHOLD = 50
SHIPPING_COST = 10
subtotal = sum(item['price'] * item['quantity']
for item in order_items)
tax = subtotal * TAX_RATE
shipping = 0 if subtotal >= FREE_SHIPPING_THRESHOLD else SHIPPING_COST
return subtotal + tax + shippingKey Changes:
AI Analysis: This is a semantic-preserving refactoring with NO logic changes. Changes detected: (1) Function renamed for clarity (calculate_total → calculate_order_total), (2) Type hints added (list[dict] → float), (3) Docstring added for documentation, (4) Magic numbers extracted to constants (TAX_RATE, FREE_SHIPPING_THRESHOLD, SHIPPING_COST), (5) For loop converted to sum() with generator expression (same functionality), (6) Shipping condition inverted but logically equivalent. **Impact:** Improved readability and maintainability. No behavioral changes. No breaking changes. Safe to deploy. Traditional diff tools would show many lines changed, but AI recognizes these are code quality improvements that preserve original functionality.
Example 2: Cross-Language Semantic Comparison
function findMax(numbers) {
if (!numbers || numbers.length === 0) {
return null;
}
let max = numbers[0];
for (let i = 1; i < numbers.length; i++) {
if (numbers[i] > max) {
max = numbers[i];
}
}
return max;
}def find_max(numbers):
if not numbers:
return None
return max(numbers)Key Changes:
AI Analysis: Cross-language comparison shows **semantically equivalent** implementations with different approaches. JavaScript version: (1) Manual iteration with index-based loop, (2) Explicit null check for empty array, (3) Imperative style with mutable max variable, (4) 11 lines of code. Python version: (1) Uses built-in max() function, (2) Pythonic truthiness check (not numbers), (3) Functional style, (4) 3 lines of code. **Functional Equivalence:** Both return None/null for empty input, both find maximum value correctly. **Key Difference:** Python leverages language built-ins for conciseness. **Migration Note:** Logic is preserved, but Python version is more idiomatic and efficient. This cross-language comparison helps verify feature parity during language migrations.
Frequently Asked Questions
Traditional diff tools show line-by-line text differences. AI code comparison understands semantics: it identifies functional changes vs cosmetic formatting, detects renamed variables that preserve logic, recognizes refactored code with identical behavior, highlights algorithm changes, spots breaking changes vs backward-compatible updates, and explains the impact of changes on performance, security, and functionality.
The AI detects multiple difference types: syntax changes (formatting, whitespace), semantic changes (logic modifications), structural changes (refactoring, reorganization), functional changes (new features, removed features), performance changes (algorithm optimization), security changes (vulnerabilities added/fixed), API changes (breaking vs non-breaking), and behavioral changes (edge case handling, error handling updates).
Yes. The AI can compare semantically equivalent code written in different languages. For example, compare a Python implementation with its JavaScript equivalent to verify logic parity, identify implementation differences, check algorithm consistency, and ensure feature completeness across multi-language codebases or during language migrations.