Best duplicate file checker for quickly finding duplicates on Windows or Mac?

You can use ​​PowerShell​​ or ​​Command Prompt (CMD)​​ to find duplicate files by comparing ​​file names, sizes, or hashes​​.

Method 1: Find Duplicates by File Name & Size (Fast but Less Accurate)​​

Get-ChildItem -Recurse -File | Group-Object Name, Length | Where-Object { $_.Count -gt 1 } | Select-Object -ExpandProperty Group | Format-Table FullName

​​What it does:​​ Lists files with the ​​same name and size​​ in a folder and its subfolders.

Limitation:​​ Different files can have the same name/size, so this isn't foolproof.

Method 2: Find Exact Duplicates Using File Hashes (MD5/SHA1) (Most Accurate)​​

Get-ChildItem -Recurse -File | Group-Object { (Get-FileHash $_.FullName -Algorithm MD5).Hash } | Where-Object { $_.Count -gt 1 } | ForEach-Object { $_.Group | Select-Object FullName, Hash }

​​What it does:​​

• Scans all files recursively.
• Computes an ​​MD5 hash​​ (unique fingerprint) for each file.
  Groups files with identical hashes (true duplicates).

No duplicate file checker required. It is a bit slower but 100% accurate​​ since even renamed files are detected.