XDA ran a piece arguing an old phone beats a Raspberry Pi for most small home-server jobs: it has a battery, a screen, a modem, and a case, all for less than a new Pi 5 kit. If the plan is to reuse an old Android phone as a small NAS for photo backup, family file sharing, or a spare place to sync a Syncthing folder, these apps do the work without root. Add a case, a fast charger set to trickle mode, and you have a headless server that survives power blips.
What to look for in an Android NAS app
- Runs without root, so you do not have to unlock the bootloader on an old phone
- Talks to phones and desktops equally well: SMB, WebDAV, or FTP so Windows, macOS, and Linux clients all mount it
- Uses external SD card storage if the phone has a slot
- Wakes on network activity or runs a persistent foreground service you can trust
- Small memory footprint, so the ancient phone does not thermal-throttle
- Auth: at minimum a password, and preferably TLS
Quick comparison
| App | Best for | Platforms | Free plan | Starting price | Rating |
|---|---|---|---|---|---|
| Primitive FTPd | FTP and SFTP file server | Android | Yes | Free | 4.6 |
| Syncthing | Peer-to-peer folder sync | Android, desktop | Yes | Free | 4.7 |
| Termux | Full Linux userland for headless jobs | Android | Yes | Free | 4.6 |
| SimpleSSHD | Lightweight SSH server | Android | Yes | Free | 4.5 |
| Nextcloud | Self-hosted file, photo, and calendar app | Android, desktop | Yes | Free | 4.4 |
| PhotoSync | Automatic photo transfer to other devices | Android | Yes | $6.99 one-time | 4.5 |
The apps
1. Primitive FTPd – Best FTP and SFTP server for Android
Primitive FTPd is the small, open-source Android FTP server that most home-lab writeups end up recommending. It handles anonymous or password auth, TLS on FTP, SFTP with an SSH key, and it can serve files from internal storage, external SD, or a USB OTG drive. A “public share” toggle exposes a folder read-only for quick guest access.
Where it falls short: The UI is minimalist. There is no built-in web viewer, so clients need an FTP or SFTP mount to browse.
Pricing:
- Free: Open-source
- Paid: None
Platforms: Android
Bottom line: Start here. It is the workhorse for exposing the phone’s storage over the network.
2. Syncthing – Best peer-to-peer folder sync
Syncthing for Android turns the phone into a node in a Syncthing mesh. Point it at a folder, share the folder ID with your laptop or another phone, and files sync both ways whenever both devices are on the same network. No cloud, no account, no bandwidth cap.
Where it falls short: Battery-friendly modes can pause sync unpredictably. Very large libraries need patience on the first scan.
Pricing:
- Free: Open-source
- Paid: None
Platforms: Android, Windows, macOS, Linux
Bottom line: The right pick for keeping folders on the phone identical to folders on other machines.
3. Termux – Best full Linux userland for headless jobs
Termux installs a minimal Linux environment on Android with apt and access to a broad package repository. You can run rsync, rclone, samba, a small web server, or a python script that watches an inbox and drops attachments into a folder. Bind a persistent notification, add a wake-lock, and Termux keeps its jobs alive.
Where it falls short: Google Play version is behind. Install the F-Droid or GitHub build for the latest packages. Requires more setup than the other apps here.
Pricing:
- Free: Open-source
- Paid: None
Platforms: Android
Bottom line: The escape hatch for anyone who wants a real shell on the phone.
4. SimpleSSHD – Best lightweight SSH server
SimpleSSHD exposes SSH on a port of your choice with key or password auth. It is much lighter than Termux for the same job, useful when you only need remote shell and rsync access without a full Linux userland.
Where it falls short: No package management. If you want extra tools, install Termux instead.
Pricing:
- Free: All features
- Paid: None
Platforms: Android
Bottom line: For the case where a shell and rsync cover the whole need.
5. Nextcloud – Best self-hosted app suite
Nextcloud for Android is the phone client for a Nextcloud server, but you can also run the server on a rooted phone or through Termux with nextcloud-cli. If your NAS ambitions include calendar, contacts, and shared editing rather than just files, this is the way.
Where it falls short: The full server on a phone is a stretch. Most people use the phone as a Nextcloud client and run the server on a small Linux box.
Pricing:
- Free: Open-source
- Paid: Optional managed hosting
Platforms: Android, iOS, Windows, macOS, Linux
Bottom line: Skip this on the server phone unless you know why you want it there. It is a client, not a NAS OS.
6. PhotoSync – Best automatic photo transfer
PhotoSync replaces Google Photos backup for anyone using a phone as a photo hub. Point the phone at a Windows or Mac target on the same network, set the wireless direction, and every new picture and video copies over in the background. It supports SMB, WebDAV, FTP, and Nextcloud as destinations.
Where it falls short: Some destination types need a one-time paid unlock inside the app.
Pricing:
- Free: Basic transfer to select destinations
- Paid: $6.99 one-time for premium destinations
Platforms: Android, iOS
Bottom line: Turns the phone into a home-network photo backup target for other family devices.
How to pick the right one
Start with Primitive FTPd to expose the phone’s storage over the network with a real password. Add Syncthing if you also want files to appear on a laptop or another phone without extra work. Install SimpleSSHD for a small SSH endpoint, or jump straight to Termux if you know you will need rsync, cron, and package management. Layer Nextcloud on top only if you plan to run the actual server elsewhere and use the phone as a client. PhotoSync covers the last mile for anyone using the phone as a landing zone for family pictures.
Set the phone to stay awake while charging, disable adaptive battery for the server apps, and pick a plug that has been proven safe on a long-running charge. An older phone can hold its own for a family-size NAS for years.
FAQ
Do I need to root the phone to run a NAS server on it?
No. Every app on this list runs unrooted. Root only helps if you want to give an app permissions Android normally reserves, or if you want to reduce battery wake-locks.
Will running a server all day damage the phone battery?
Modern Android phones tolerate constant charging better than older ones because they cap charging at 80 or 90 percent when kept plugged in. Use a good charger, keep the phone cool, and expect the battery to still eventually degrade after a few years.
Which app is the fastest for transferring large files?
Primitive FTPd over SFTP or Termux with rsync will be the fastest on the same LAN. SFTP tends to hit the phone’s storage speed limit before it hits Wi-Fi.
Can I use the phone as a Time Machine target for a Mac?
Yes, through Netatalk in Termux, but the setup is finicky. For most people, a Raspberry Pi or a small NAS is a better Time Machine host than a phone.
What if the phone gets a call while it is serving files?
An Android phone still takes calls in the background. Serving files does not block the modem. If you want an actual headless server, remove the SIM and use Wi-Fi only.
