The short answer: if several people need the library at once, a Wi-Fi box like the Prepper Disk Premium ($297) is the easiest. If you're handy and want it free, build your own with Kiwix or Internet-in-a-Box. If you want a ready drive with survival guides and your state's maps, get the Grid-Down Pocket Drive ($149). That last one is ours.
Disclosure: we make the Grid-Down Kit. We've tried to judge it by the same rules as everything else here, and we say where the others are the better buy. Prices are as listed on each maker's site on 3 November 2026.
Quick picks
| Best for | Pick | Price |
|---|---|---|
| A whole household sharing one library over Wi-Fi | Prepper Disk Premium | $297 |
| Free, if you're comfortable setting it up | Kiwix (app + downloaded library files) | Free |
| Schools, clinics and tinkerers | Internet-in-a-Box | Free software; you supply a Raspberry Pi |
| A ready drive with survival guides, your state's maps and offline AI | Grid-Down Kit Pocket Drive (ours) | $149 |
| You already own a big drive | Grid-Down Kit Digital (ours) | $99.99 |
How we judged them
- Works with no internet and no cell signal. All five do, once they're set up.
- Power. Does it need its own power, or does it run from the laptop or phone you already have?
- Setup. Can a non-technical person get it working in a few minutes?
- What's on it. Is it a general library (Wikipedia, medical wikis, maps), or does it also tell you what to do in an emergency, step by step?
- Sharing. Can more than one person use it at the same time?
Prepper Disk Premium: best for sharing with a household
It's a small Raspberry Pi computer in an aluminum case with a 512 GB card. It broadcasts its own Wi-Fi network, so phones, tablets and laptops can join and browse the library at the same time. The maker says about 19–20 devices can connect at once. It carries the full English Wikipedia, offline medical manuals, FEMA preparedness guides and maps (Prepper Disk product page).
- Good: nothing to install on your devices; everyone in the house can use it at once; no subscription.
- Watch out: it needs its own power, so keep a USB-C power bank with it. The maker recommends powering it on once or twice a year to check the card.
- Buy direct: we found other websites using the Prepper Disk name and offering it at 70% off. We can't vouch for them. The maker's store is prepperdisk.com.
Kiwix: best free option
Kiwix is a free, open-source reader for offline copies of websites. You install the app on a computer or phone, then download the library files you want, such as Wikipedia or medical wikis. It's the engine underneath most of the products on this page, including ours.
- Good: free; runs on Windows, Mac, Linux, Android and iPhone; you choose exactly what to store.
- Watch out: you do the choosing, downloading and checking yourself. The big files take hours to download, and you need a drive with plenty of room. Kiwix gives you a library, not an emergency plan.
Internet-in-a-Box: best for schools, clinics and tinkerers
Internet-in-a-Box is free, open-source software that turns a Raspberry Pi into an offline "learning hotspot". It serves Wikipedia, Khan Academy videos, OpenStreetMap and e-books to any phone nearby over Wi-Fi (project description). It runs in over 100 countries, mostly in schools and clinics, on volunteer labor and grants (BGR).
- Good: free software; very flexible; built for places with no internet at all.
- Watch out: you build it yourself. It's a project for an afternoon or a weekend, not a plug-in product.
Grid-Down Kit Pocket Drive: best ready drive with survival guides and maps (ours)
A 256 GB USB drive, already built. It holds the Grid-Down app, which walks you through 18 emergency situations with no internet. It also has The Field Manual and every kit guide, about 180 GB of offline library (English Wikipedia, WikiMed, MDWiki, WikEM and public-release manuals), the US street map with your state's map data, and an offline AI model.
- Good: no extra box to power, because it runs on the laptop or phone you plug it into. It tells you what to do in an emergency, not just where to read about it. The maps are for your state. Every library file is checked against its publisher's checksum.
- Watch out: it's a drive, not a Wi-Fi hotspot. One device uses it at a time unless you share it from a laptop. Older iPhones need an adapter, and the offline AI is small and makes mistakes. Check safety steps against the printed guide. It's built to order and ships in 5–10 business days.
See the Pocket Drive · The 1 TB Core Drive adds every USGS topo map and the water data for your state, plus the printed Field Manual ($349).
Grid-Down Kit Digital: best if you already own a big drive (ours)
The same app, guides and Field Manual as a download. It also includes a builder that puts the offline library, maps and AI onto a drive you already own ($99.99). You need internet while it builds, and a drive with room for what you choose. See the Grid-Down Kit.
Side by side
| Prepper Disk Premium | Kiwix | Internet-in-a-Box | Grid-Down Pocket Drive | |
|---|---|---|---|---|
| Price | $297 | Free | Free + your hardware | $149 |
| Setup | Plug in, join its Wi-Fi | Install, download, organize | Build it yourself | Plug in |
| Own power needed | Yes | No | Yes | No |
| Several people at once | Yes, about 20 | No | Yes | Via a laptop |
| Step-by-step emergency guides | FEMA guides included | Only what you add | Only what you add | Yes, 18 situations + Field Manual |
| Maps | Yes | Only what you add | OpenStreetMap | US streets + your state |
What none of them replace
- Paper. Screens die. Keep a printed copy of your household plan and the one rule for each emergency you're likely to face. Our free Your First 72 Hours guide prints on 12 pages.
- Power. Every device here needs a charged battery to be useful. A power bank does more than any library.
- Practice. Open it once before you need it. A library you've never used is a library you won't find your way around in the dark.
- Your local alerts. Turn on Emergency Alerts on every phone. Then read the survival guides for the hazards where you live.
Questions people ask
Can I build a prepper drive myself for free?
Yes. Install Kiwix and download the library files you want onto a large drive. The cost is a drive and a few hours of downloading and checking. The paid options sell you the time, the curation and the testing, not the content, which is open and free to copy.
Which is better: a Wi-Fi box or a USB drive?
A Wi-Fi box is better if several people need it at once and you can keep it powered. A drive is better if you want one less thing to charge, since it runs on the laptop or phone you already have.
Do these work in a blackout?
Yes, as long as the device you read on has battery. None of them need the internet or a cell signal once they're set up.