Why Substratum
Last Updated: 2026-06-11
Substratum helps families keep photos, videos, and important files in several places at once—not only on one laptop or one box in the basement.
You choose where copies live: your house, a parent's house, a sibling's house, your phone, and optionally an extra safe copy through Substratum's service. Those places stay up to date with each other. If one place fails, the files are still somewhere else you trust.
The problem
- One device — If it dies, gets stolen, or is wiped, everything on it can be gone.
- One backup drive — Easy to forget to plug in, easy to lose, easy to put in the wrong drawer.
- Only the cloud — Convenient, but your whole history lives behind one account and one company's rules.
- "Who has the real copy?" — Folders on phones, email attachments, and old USB sticks get messy fast.
Families need something simpler: the same memories in more than one home, updated quietly, with a clear answer to "Is it safe? Is it copying? Where else does it exist?"
How it works
1. Sign in with the account you already have
Sign in with your Bluesky, Tangled, or any AT Protocol handle—approve once on that service's site. No separate Substratum password. Family members can use different providers and still share by handle.
2. You pick your safe places
Typically up to three homes or devices you control or trust—for example:
- your home computer or home storage box
- a parent's storage at their house
- a sibling's old desktop that stays on
Each place runs a small home helper program that watches folders you choose and keeps them in sync with the others.
3. You can add an extra safety net
If you want, Substratum can also keep copies in secure storage run by Substratum (in more than one part of the world). That helps when houses are far apart or the internet between homes is fussy. Your home copies are still yours; the extra copies are there so you're not betting everything on one address.
4. You add and share files normally
Save a photo once. Over time it shows up in the places you allowed. Share an album with your brother or a folder with your parents—only what you choose, not your whole library.
5. You see status, not guesswork
A simple view tells you things like:
- which places are online
- which are still copying
- which need attention (disk full, unplugged, offline too long)
- where important items still have a copy if one place has a problem
That last part is the peace of mind: "Mom's box died, but we still have the wedding photos at your sister's and at ours."
A few days in the life of a family
Saturday — new photos from the party
You import pictures on your laptop. By evening they're on your home storage. Overnight they finish copying to your parent's and your sibling's. You don't email zip files to everyone.
Tuesday — a home storage box acts up
The app shows that place as needs attention, not "everything is lost." You still open files from your house and your sibling's. You fix or replace the box when someone has time.
Holiday — share with siblings
You share a reunion album. Each sibling sees only that album in their own space. Nobody gets access to your tax folder unless you share it.
Who does what
| Person | Role |
|---|---|
| The household helper (often one tech-comfortable person) | Sets up the home program, picks folders, sets how much disk each place may use, checks status |
| Everyone else | Signs in, adds photos, browses shared albums |
| Extended family | Sees only what was shared with them |
How this differs from "just the cloud"
| Usual cloud photo app | Substratum | |
|---|---|---|
| Where files live | Mostly on their servers | In your homes you control, plus optional extra copies |
| If the company changes rules | You adapt | Your copies still sit in places you chose |
| If one home has a fire or dead drive | Often "we lost the local copy" | Other homes still have it |
| Who can see everything | Whoever has the one account | Only people and places you invited |
| Sign-in | Another email and password | Your existing Bluesky, Tangled, or AT Protocol handle |
Privacy and trust
- Copies move only between places you set up or people you invited.
- Random people on the internet cannot browse your family library.
- Sharing is on purpose—an album, a folder—not "everything public."
- The person who runs storage at each house controls how much space is used so one machine doesn't get silently filled.
What you need at home
- At least one place that stays on (a home storage box, a small always-on computer, or similar).
- Internet that's good enough for background copying (doesn't have to be perfect every minute).
- One person willing to do a one-time setup per home; after that, daily use feels like normal folders and a simple app.
Questions families ask
Is this like Dropbox or iCloud?
Those keep your stuff mainly on their machines. Substratum is built so your copies live in homes you trust, with optional extra copies for safety—not "one basket."
Do my siblings see all my files?
No. Only folders or albums you share.
What if we live in different cities?
Homes can still sync over the internet; the optional Substratum safety copies help when home-to-home copying is slow or interrupted.
What if nobody is technical?
One person sets up each home once. Everyone else uses familiar ideas: folders, albums, share with family.
Learn more
- Business model — pricing, free vs paid paths, and what we commit to publicly
- Getting started — for the person setting up storage at home
- Technical specification — for builders and operators
- The intergalactic web — essays on ownership, privacy, and permissions on the distributed web
- Substratum on Open Collective — the open-source distributed persistence layer vision