Paid cloud photo storage is convenient but recurring, and most free tiers (5–15GB) fill up within a year of regular phone use. An automatic local backup — to a computer you already own, or a home NAS — costs nothing ongoing and has no arbitrary storage ceiling beyond your own drive space.
01iPhone → Windows PC (automatic, wired or Wi-Fi)
The Photos app on Windows can auto-import from a connected iPhone. For a fully automatic wireless version, iCloud for Windows can be set to only download originals to a local folder without keeping them in iCloud long-term — under iCloud Photos settings, choose "Download Photos and Videos" without "Upload."
02iPhone → Mac (automatic, no cables after first setup)
Photos app on Mac: Photos → Settings → iCloud → uncheck "iCloud Photos," but enable "Import to: [a folder of your choice]" under File → Import preferences won't auto-run without the app open — instead, keep Photos app set to auto-launch when your iPhone connects, or use the free app "Image Capture" (built into macOS) with its own auto-import folder set for wireless transfer over the same Wi-Fi network.
03Android → any computer
Android's built-in "USB file transfer" mode lets File Explorer or Finder see your phone as a drive — the DCIM folder holds your photos. For automatic wireless sync without cables, the free and open-source Syncthing app runs on both your phone and computer, watching your camera folder and copying new photos over your home network the moment they're taken, with no cloud step in between at all.
04The more resilient option: sync to a home NAS
If you have a NAS (Synology, QNAP, or a self-built one), both platforms offer free companion apps — Synology Photos and QNAP QuMagie — that auto-upload from your phone over Wi-Fi whenever you're home, giving you a backup that survives even if your main computer fails, since it's a separate device.
05Follow the 3-2-1 rule even with a free setup
A single local backup is much better than none, but it's still one point of failure (fire, theft, drive failure). The standard practice: 3 copies of your data, on 2 different types of storage, with 1 copy offsite. A practical free version: phone (copy 1) → computer (copy 2, different storage) → an external drive kept at a different location, like a relative's house, updated every few months (copy 3, offsite).