Developer
How to Compare Text and Code — Diff Tools Explained
Learn how to use diff tools to compare text, code, and documents. Find changes quickly with our free online diff checker.
Diff (difference) tools are essential for anyone who works with text, code, or documents. They show you exactly what changed between two versions.
What Is a Diff?
A diff is a comparison between two pieces of text that highlights:
- Added lines — New content that wasn't there before
- Removed lines — Content that was deleted
- Unchanged lines — Content that stayed the same
Common Use Cases
1. Code Review
// Original
function greet(user) {
return "Hello, " + user;// Modified
function greet(user) {
return 'Hello, ' + user + '!';
}
`
Diff shows the return statement changed.
2. Document Comparison
3. Configuration Files
4. Data Comparison
How to Read a Diff
| Symbol | Meaning | Color |
|---|---|---|
| + | Line added | Green |
| − | Line removed | Red |
| (none) | Unchanged | Default |
Best Practices
- Compare line by line — Most diff tools show side-by-side or inline views
- Check context — Always look at surrounding lines, not just the change
- Watch for whitespace — Some diffs ignore whitespace, others don't
- Use for code review — Always diff before merging code
Online vs Offline Diff Tools
| Feature | Online (FreeToolJet) | Offline (Git, IDE) |
|---|---|---|
| No install | ✅ | ❌ |
| Any device | ✅ | ❌ |
| Version control | ❌ | ✅ |
| Large files | Limited | Better |
| Privacy | Browser-only | Local |
Our free diff checker runs entirely in your browser — your text never leaves your device.