📊 Text Diff Checker

Compare differences between two texts

Original text

Text to compare

What is Diff?

Why use diff?

Diff highlights additions, deletions, and modifications between two texts or files. It quickly surfaces changes for code reviews, document comparison, and config validation.

Version control systems like Git and SVN rely on diff algorithms to track commits. Developers use diffs to understand impact, avoid mistakes, and review faster.

When to use it

Code review: inspect Pull Request changes
Config compare: dev/prod config differences
Document versioning: before/after comparison
API response compare: expected vs actual
Migration checks: before/after data moves
Merge conflicts: inspect both sides in Git

Practical examples

Example 1: Config file comparison

Dev environment (config.dev.json)

{
  "database": "dev_db",
  "port": 3000,
  "debug": true
}

Prod environment (config.prod.json)

{
  "database": "prod_db",
  "port": 8080,
  "debug": false
}

Diff: database, port, and debug values differ

Example 2: Code change

- function calculateTotal(items) {
+ function calculateTotal(items, discount = 0) {
  let total = items.reduce((sum, item) => sum + item.price, 0)
+  total = total * (1 - discount)
  return total
}

Signature updated and discount logic added

Diff notation

Mark	Meaning	Description
+ line	Added	New content was added
- line	Deleted	Content was removed
~ line	Modified	Content was changed
line	Unchanged	No change (context)

Caveats

Whitespace/indentation: whitespace-only differences still count. Run a formatter first.
Line endings: beware of Windows (CRLF) vs Unix (LF).
Large rewrites: if everything changes, the diff is less meaningful.
Binary files: images/PDFs cannot be compared with line diff.
Encoding: different encodings can make identical content appear different.