Safer Internet: Offline: Erasing Your Device

Summary | Apps | Device | Files | Redacting |
References: General | Android | iOS | macOS | Photos |
Recycling/Reselling | Redacting | Windows

Summary

[2] Erasing Apps -- and associated settings, and maybe data

  • Removing an unused app can free up storage, and reduce software update nags
  • To find out how much storage is used on your device: (esp. for apps, movies, videos, podcasts, music, photos, iOS backups)
  • iOS10: Settings > General > Storage&Cloud Usage > Storage > Manage Storage
  • iOS: Settings > General > iPad/iPhone Storage: Offload Unused Apps; iCloud Photo Library; individual apps
  • iOS: Settings > iTunes & App Store: Offload Unused Apps
  • macOS: [apple] > About This Mac > Storage > Manage
  • To remove not only an app, but also its settings, storage caches, etc.:
  • iOS: press down on app icon to enter move / delete ('jiggly') mode
  • tap "x" in upper left corner
  • popup: "Deleting (app) will also delete all of its data"
  • (press Home button to exit 'jiggly' mode)
  • To immediately delete related iCloud data:
  • iOS10: Settings > iCloud > Manage Storage > (device) > disable old app
  • iOS: Settings > (your acct) iCloud > Manage Storage > (app) > Delete Documents & Data
  • macOS: just dragging an app (from Applications folder) to Trash does not remove extra preference/library files
  • Use app's uninstaller (if one is provided) or an app removal utility, e.g., App Cleaner
  • [2] macOS: 3rd party utilities can find duplicate and large files, e.g., Disk Cleanup Pro (free; in the Mac App Store)
    "Disk Cleanup Pro automatically cleans up the big offenders, Caches and Logs, plus it allows you to scan for duplicate files and large files. You can set the threshold for file size (e.g. bigger than 50 MB) in preferences, and can set separate thresholds for different types of files (Movies, Photos, Text, etc.). It tells you broadly what type of file it is dealing with (Photos, Music, Documents, etc.); fileinfo.com can help you identify the kind of file for a file extension you don't recognize." ~Peter DeGroot, AshMUG
  • [3] macOS: (select files/folders) > File (ctrl-click) > Compress -- to reduce size of files you want to keep, but access infrequently; rename .zip if desired; delete originals when done
  • [3] macOS: Monolingual removes unused languages (and processor architectures) from System/Apps , e.g., just keep English yields ~2Gb
  • [3] macOS: (HD/SSD) : "Previous System" folder (if present: ~1-2Gb) can be deleted, but it can be very difficult/tricky to actually Empty Trash

[2] Securely Erasing Device / Disk

  • Securely erase drive before donating, discarding, recycling, selling or transferring your device; to be nice, re-install OS
  • This assumes that you've already backed up anything you care about, and migrated files/settings to any new device.
  • iOS: Settings > General > Reset > Erase All Content and Settings
  • Trigger auto-erase if lost or stolen?
  • iOS: Settings > Passcode > (passcode) > Erase Data -- after 10 failed passcode attempts
  • iOS: Settings > (your acct) > iCloud > (device) > Find My iPhone/iPad -- allows you to erase remotely
  • [3] macOS: erase disk and install OS
  • Boot from Recovery Partition (option-R during Restart); or your bootable clone; for older macOS, boot from DVD or USB
  • Utilities: Disk Utility > (select drive) > Erase -- generally use Format: Mac OS Extended (Journaled) (for now, don't use High Sierra's APFS); for older macOS, and non-SSD, use option to Erase Free Space: 3 (or more times), if available
  • Utilities: Reinstall macOS/OS X

[3] Securely Erasing Files

  • Even if you empty Trash / Recycle Bin, various utilities might be able to recover file content -- unless it's encrypted.
  • macOS: (≥ 10.10) use FileVault: erased file sectors are still encrypted -- thus unreadable; see Encryption section
  • macOS (< 10.10): Finder > Secure Empty Trash

[3] Redacting Files

  • Some source files (e.g., .doc, .pdf, .jpg) can retain layers / versions of info, i.e., metadata, or track changes;
    it might be recoverable via copy/paste or tools; just deleting it or overlaying an annotation may not be enough!
  • So, omit sensitive info from files in the first place: content as well as metadata such as Author, Organization
  • or, save edited document or selected screen area as an image
  • or, copy/paste selected (non-sensitive) info into a simpler format, i.e., one that removes any hidden info -- or use redaction tools
  • Remove photo metadata; e.g., phone location via iOS: Photo Investigator
  • Redact a .pdf or source document to remove sensitive info -- using proper tools, i.e., Adobe Acrobat Pro; otherwise, simple annotations / changes can be selected, copied, revealed

References

Android

iOS

macOS

Photos

Recycling / Reselling

Redacting

Windows