Question 1

What is a diff checker?

Accepted Answer

A diff checker compares two texts and highlights exactly what changed between them — added lines (in green), removed lines (in red), and unchanged lines. It is commonly used by developers to review code changes, compare configuration files, spot edits in documents, or debug API response differences.

Question 2

What algorithm does this diff tool use?

Accepted Answer

This tool uses the Longest Common Subsequence (LCS) algorithm — the same foundation as Unix diff, Git diff, and most professional diff tools. It finds the minimum number of insertions and deletions needed to transform the original text into the new text, producing the most accurate and readable diff output.

Question 3

Is my text sent to a server?

Accepted Answer

No. All comparison happens entirely in your browser using JavaScript. Your text never leaves your device and is not sent to any server, stored, or logged. This makes it safe to use with sensitive data like configuration files, API keys, or private documents.

Question 4

What is the difference between line diff and character diff?

Accepted Answer

Line diff (the default) compares entire lines and marks each changed line as added or removed. Character diff goes deeper, highlighting which specific characters changed within each line. Line diff is better for code and config files; character diff is better for prose or single-line changes.

Text Diff Checker

Text Diff Checker — How It Works

Common Use Cases