Anyone know a good file shredder for mac for permanent data deletion?

Completely wiping the hard disk in macOS recovery mode is done by using Disk Utility or terminal commands. Physically overwrite and reconstruct the hard disk to ensure that the original data cannot be recovered by software. Most importantly, no file shredder software for Mac needed for this method!

Normal Deletion vs Secure Erase

Normal Deletion: Deletes only the file index (marking the space as writable), the actual data still exists on the hard disk, and can be retrieved by scanning the magnetic tracks with recovery tools.
Secure Erase: Writes random data through multiple overwrites (e.g., all zeros, all ones, or other patterns), destroying magnetic traces of the original data, and is compliant with military/financial-grade security standards (e.g., DoD 5220.22-M).

Solid State Drives (SSD) Specificity

SSDs may be physically dispersed due to wear-leveling mechanisms, but macOS secure erase triggers the controller to perform TRIM + encryption key destruction (if FileVault is enabled). (if FileVault is enabled), making it impossible to decrypt the data.

Advantages of Recovery Mode

Operate independently of the system environment to avoid incomplete erasure due to system file occupation.

Direct access to the bottom layer of the disk, supports full disk coverage (including hidden partitions).

You don't need any file shredder software for Mac if you want to try this approach.