Diff Checker Online — Compare Files and Text Side by Side

Diff Checker Online A diff checker online tool compares two text blocks and shows exactly what changed — added lines in green, removed lines in red, and the unchanged context around them. No terminal, no git diff, no editor setup. Paste and compare. This guide covers how diff algorithms work, how to use diff in code, and the best free tools for everyday code comparison tasks. What Is a Diff? A diff computes the minimum set of changes needed to transform one text into another. The output marks each line as: Added (+) — exists in the second version only Removed (-) — exists in the first version only Unchanged — exists in both versions Example: Simple Diff Version A: function greet(name) { console.log("Hello, " + name); return true; } Version B: function greet(name, greeting = "Hello") { console.log(`${greeting}, ${name}!`); return true; } Diff output: - function greet(name) { + function greet(name, greeting = "Hello") { - console.log("Hello, " + name); + console.log(`${greeting}, ${name}