First: stop using the drive
Deleted files aren't erased immediately — the space is just marked reusable. Every new file you save can overwrite them. So the single most important step is to stop writing to the affected drive right away. If it's an external drive, unmount it until you're ready to scan.
Step 1 — Download and open Cinder
Install Cinder Data Recovery and launch it. Scanning and previewing are free — you don't need a license or an account to see what's recoverable.
Step 2 — Pick the drive and a scan type
Quick Scan reads filesystem metadata that's still on disk, including files sitting in the Trash. It's fast and catches recently-deleted files. Deep Scan also carves raw sectors for files the filesystem has already forgotten — slower, but far more thorough for files deleted a while ago or lost to a format.
Step 3 — Preview before you pay
Results show up with their original filenames and folder paths, not generic reconstructions. You can preview photos, audio, and video inline. This is the moment to confirm the files you care about are really recoverable — before spending anything.
Step 4 — Recover to a different drive
When you save files, write them to a different drive than the one you're recovering from. Recovering onto the same drive can overwrite other deleted files you haven't gotten to yet.
The one case that won't work: your startup disk
Deep recovery of already-deleted data from your Mac's own startup disk is blocked by macOS System Integrity Protection — for every recovery tool, not just Cinder. To deeply recover a startup disk, you boot from another drive (or macOS Recovery) and scan it "from outside." Quick Scan still works on the startup disk for files the filesystem remembers.