Diff Checker — How to Compare Text & Code
Learn how to compare text, code, and JSON files. Use our Diff Checker tool to find differences side by side.
What is a Diff?
A diff (short for difference) shows the changes between two files or texts. It highlights additions, deletions, and modifications line by line. Diffs are essential for code review, version control (git), debugging configuration changes, and tracking document revisions.
Diff Output Formats
--- original.txt +++ modified.txt @@ -1,5 +1,6 @@ line 1 -line 2 (removed) +line 2 (replaced) line 3 +new line 4 line 5 -line 6 (deleted)
Original
line 1 line 2 (removed) line 3 line 5 line 6 (deleted)
Modified
line 1 line 2 (replaced) line 3 new line 4 line 5
Real-World Diff Examples
Before
{
"name": "John",
"age": 30,
"email": "john@old.com"
}After
{
"name": "John Smith",
"age": 31,
"email": "john@new.com",
"phone": "+1-555-0000"
}Old Version
function greet(name) {
return "Hello " + name;
}
console.log(greet("World"));New Version
function greet(name, formal) {
if (formal) return "Good day, " + name;
return "Hello, " + name;
}
console.log(greet("World", false));When to Use a Diff Checker
Frequently Asked Questions
What is a diff checker?
A diff checker compares two files or texts and highlights the differences between them — additions, deletions, and modifications — line by line. It is essential for code review, version control, and document comparison.
What is the difference between unified diff and side-by-side view?
Unified diff shows all changes in a single view with +/- markers and shared context lines. Side-by-side view splits the original and modified versions into two columns for visual comparison. Each format works best for different workflows.
Can I compare JSON files with a diff checker?
Yes. A diff checker can compare any text, including JSON, code, configuration files, and documents. For structured JSON comparison, you can also use a dedicated JSON compare tool that understands JSON syntax.
Is diff checking useful outside of programming?
Yes. Diff checkers are used for comparing document revisions, tracking changes in legal contracts, verifying configuration changes, and reviewing edited content — any scenario where you need to see what changed between two versions.
Does our diff checker send my files to a server?
No. Our diff checker processes everything locally in your browser. Your files and text are never uploaded to any server.