What Is an Air Gap?
Published 2026-08-15. Last updated 2026-08-15. Written by John Alewine, Crypto Guidance Inc.
An air gap means the machine that can spend your coins does not have a network connection, and you do not plug it into a machine that does. Data crosses the gap as a file or a QR code, not as a live USB conversation with your infected laptop. A Coldcard used with an SD card is the example I can point at. A hardware wallet permanently glued to Ledger Live over USB is convenient, and it is a thinner gap.
Who This Is For
People holding an amount they would not want sitting next to a browser. It is not required for a first $100 of bitcoin. It is the threat model behind "I am done being one malware click away."
How It Actually Works
- Computer builds a PSBT. You walk the file to the offline signer. You walk a signed file back. The computer broadcasts.
- Creating the seed should happen on the offline device, not in a website, not in a phone app that later "became" watch-only. See the restore test.
- QR air gaps (animated QR between phone and device) are still an air gap if the signer has no radio. Verify addresses on the device screen either way.
Risks I See in Sessions
- "Air-gapped" firmware updated over the same USB they swore they would never use. Occasional updates happen. Make them intentional, from official files, not a surprise cable.
- A signer that has Wi-Fi "just for the price ticker." That is not an air gap. That is a phone with extra steps.
- Photographing the seed so the gap is easier to bridge. You just put the private side on a networked camera roll.
When It Matters
Savings, inheritance, and any stack you would not keep in a hot wallet. The Security page is the spine. Coldcard plus Sparrow is one finished implementation, not the only one.
Related Terms
Glossary · Learn · Resource Library · Home