Compare Code Online
Spot Every Difference Between Two Code Snippets
Need to use Compare Code Online right now?
A line-by-line diff makes a small but critical change (a swapped variable, a removed condition) immediately visible.
Features
- Runs entirely in your browser
- Privacy-first — your data is never uploaded
- Real-time, instant results
- 100% free, no sign-up required
- Works on desktop, tablet, and mobile
- No installation needed
Who uses this tool?
About Compare Code Online
Spotting exactly what changed between two versions of a function, config file, or code snippet by eye is slow and error-prone, especially once whitespace and reordering enter the picture. This tool runs a real line-based diff algorithm (longest common subsequence) between two code blocks and highlights every added and removed line clearly, color-coded and ready to scan.
Unlike a naive line-by-line comparison, the LCS-based algorithm correctly identifies lines that moved or stayed the same even when other lines around them changed — so a single line inserted in the middle doesn't cause every subsequent line to falsely show as different, which is exactly the failure mode of simpler diff approaches.
This is genuinely useful for reviewing a colleague's proposed code change pasted outside of a proper git diff, comparing two versions of a config file, or checking exactly what an AI tool or refactor changed in a function without needing a full version control setup.
How it works
- Paste original code. The starting version of your snippet.
- Paste modified code. The changed version to compare against.
- Review the highlighted diff. Added lines in green, removed lines in red.
Examples
Comparing two function versions
Input
Original vs. refactored function
Output
Line-by-line diff showing exactly what changed