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); +