I had an old Google Pixel 3a XL sitting around and decided to see if it could handle running as a fully offline, self-contained web server.

I flashed postmarketOS 26.06 (headless Alpine Linux base) to it and set up a portable media node that broadcasts its own Wi-Fi AP, serves static pages, and streams video over a captive portal - no cell data or upstream internet needed.

Quick Hardware/Tech Stack Breakdown:

• Device: Google Pixel 3a XL (2019)
• OS: postmarketOS 26.06 (CLI base with OpenRC)
• Networking/AP: hostapd for the AP, dnsmasq for DHCP & wildcard DNS routing
• Firewall: nftables redirecting port 80 requests to trigger the captive portal popup automatically
• Web Server: Lighttpd handling HTTP requests and MP4 video range requests

Performance & Power Draw: Under a test load streaming 720p video to 4 concurrent devices, total CPU usage averaged around 5% (load avg 0.51). Power draw stayed around ~2.4W off the internal battery, with temps holding steady at 54°C.

Why build this? Mainly as an offline entertainment and information node. I run a non-profit foundation providing SCUBA training to young survivors of childhood abuse, and having a tiny, battery-powered web node lets us provide offline information and videos to people while traveling. I will also be able to use it to provide training videos if I am teaching in a location that does not have internet access available.

I wrote up a complete overview covering the setup, and performance metrics if anyone wants to replicate it or build something similar. Over the coming weeks I will be posting configs and some other information to Github with a link from my site.

https://www.muttmutt.us/geeky-stuff/portable-web-server-on-an-android-phone-for-offline-access/

Happy to answer any questions about postmarketOS setup or the networking config!

I use my 3a as GPS using Lineage OS and a Wi-Fi hotspot

I've used older phones for a lot of things like that. I have a couple that I use for bedroom HomeAssistant controllers, along with a couple tablets for near the front and back doors. I have an LG V20 I have been tinkering with so that I can power it without a battery at all but that is a bit of a pain.

I have seen projects where phones have been turned into vehicle dash camera's that once connected to WiFi will upload to the home server. There are a ton of other things you can do with an old phone if you just find a way to use it. The bad thing is that a lot of the older phones are stuck on the OS they have with no chance of another update or ability to change the OS for other uses.

It was fun! I'd never done any kind of sideloading or customization of a phone prior. I learned a lot from the experience. Similar getting the Jellyfin app to run on a Samsung TV. I'd like to eventually convert my old laptop into an automotive diagnostic reader, with the ability to add/delete keys via the OBDII port. That's a big project tho, lots of moving parts

Thanks for the write-up on your post, very informative 😁♥️

Just grab an ELM327 Bluetooth OBD II adapter and Torque for Android. At night it can easily be used as a heads up display and if you get the window cling for the heads up displays you can use it in the daytime too.
It won't add or remove keys but it works great for data logging and diagnostics.

I have that, it's pretty neat. I want to see what I can get into regarding keys in party because I'm a commercial door locksmith that is bi-specialty curious

Ahh I understand. I only have one vehicle that uses electronic keys so I bought an OBD II adapter from a place vs taking it to a shop. I highly doubt I'm going to get a different vehicle any time soon to need to add more more keys.