What is a dead man's switch?

From emergency brakes to encrypted messages

The original dead man's switch was physical: a lever on a train that had to be held down by the driver, so the brakes would engage if the driver ever let go. The idea carried over to machinery, industrial equipment, and eventually software — any system designed to act when a person can no longer act themselves.

A digital dead man's switch applies this idea to communication. Instead of stopping a machine, it releases information: final messages, account details, instructions, or documents that would otherwise be lost or locked away if something happened to you.

How a digital dead man's switch works

Modern dead man's switch apps are built around check-ins. You confirm you're okay on a schedule you choose — for example once a week or once a month. Each check-in resets the timer.

If you miss a check-in, the system doesn't fire immediately. You get reminders across multiple channels, and only after a grace period with no response does the switch consider you unreachable. At that point it delivers your prepared messages to your chosen recipients.

What people use one for

• Final messages

  Letters to a partner, children, or friends that should only be read if you're gone.

• Practical information

  Where important documents are kept, who to contact, what needs to be cancelled or managed.

• Account access

  Instructions your family needs to reach accounts, subscriptions, and assets they would otherwise be locked out of.

• Wishes and instructions

  Funeral preferences, care instructions for pets or dependents, and anything else you want handled a certain way.

How PostMortem implements it

PostMortem is a dead man's switch built around encrypted message boxes. You write messages, attach files, and assign each box to specific recipients. Everything is encrypted on your device before it is uploaded — PostMortem's servers never see the contents.

Then you simply respond to periodic check-ins in the app. If you stop responding and don't react to the follow-up reminders, your message boxes are released to your recipients, who unlock them with the access keys you shared with them in advance. Until that moment, nothing is ever delivered — and you can check in, edit, or cancel at any time.

Why encryption matters for a dead man's switch

A dead man's switch necessarily holds your most sensitive information for a long time, so how it is stored matters as much as when it is delivered. If the service can read your messages, so can an attacker who breaches it.

That's why PostMortem uses end-to-end encryption with keys that only you and your recipients hold. Even a full copy of PostMortem's database would reveal nothing about what your messages say.