Text Diff Checker: Compare Files Like a Pro Developer

If you've ever compared two versions of a config file or code snippet, you've used a diff checker. Here's how they work and which tools to use. How Diff Algorithms Work Most diff tools use the Longest Common Subsequence (LCS) algorithm or Myers' diff algorithm. They find the minimal set of changes needed to transform text A into text B. Output types: Unified diff : Shows changes with context (git default) Side-by-side : Two columns, easy visual comparison Inline : Changes highlighted within the text Command Line Tools git diff git diff file.txt # Working vs staged git diff --staged # Staged vs HEAD git diff HEAD~3..HEAD -- file.txt # Last 3 commits diff (POSIX) diff -u file1.txt file2.txt # Unified format diff -y file1.txt file2.txt # Side-by-side colordiff colordiff -u old.txt new.txt # Colored unified diff In Code JavaScript import { diffLines } from ' diff ' ; const changes = diffLines ( oldText , newText ); changes . forEach ( part => { const prefix = part . added ? ' + ' : part .