102 · Wallet configuration · lesson 1 of 4

Hot and cold — where savings belong

Before you choose how your keys are arranged, decide which money you are arranging them for. Everything in this level follows from one distinction — whether a wallet’s keys are reachable from the internet — and from the decision that distinction forces: how much of your Bitcoin sits on each side of it.

What hot and cold actually mean

A wallet is hot when its keys sit on something connected to the internet, and cold when they don’t. A phone app, a desktop app, a browser wallet — all hot. Your keys there may be encrypted and locked behind a fingerprint, but the device is still online, so it’s reachable by whatever reaches any online device: malicious apps, phishing, remote attacks.

A cold wallet keeps the keys on a device that stays offline — usually a hardware wallet. An attacker gets only a few narrow moments at it: when you first set it up, when you sign a payment, and when you recover it. The rest of the time it is simply out of reach. That’s the whole advantage, and it’s a big one.

Think of it as a spectrum rather than a switch. The real question for any wallet is: at what moments could someone get in, and what would that take? Which is why the rule isn’t “cold is good, hot is bad” — it’s match the wallet to the job.

One warning that catches people: writing your seed words into a note, a photo, or a password manager instantly makes your cold wallet hot again — you’ve just put the key back on an internet-connected device. That’s rule 07, and it’s one of the most common ways people lose everything.

How much belongs at each temperature

That’s the definition. This is the part that’s actually a decision. Experienced holders rarely use one wallet for everything — they run a few, at different temperatures, and let money flow between them.

• A hot wallet holds a small amount for spending. If your phone is lost or compromised this balance could go with it — but because it’s small, that’s survivable. If you use Lightning — Bitcoin’s layer for instant everyday payments (see the glossary) — those funds have to be hot by design.
• A cold wallet — a hardware wallet — holds the balance you’re not spending this week but still want within reach. For most people this single device is the core of the whole setup.
• Deep cold storage holds the bulk, touched rarely. This is where the more involved setups in the next lesson earn their keep, and it only becomes worth the extra effort once you’re holding a substantial amount.

Money flows one way as your balance grows: income lands hot, gets swept to cold, and — once cold holds more than you need soon — moves to deep cold. Spending reverses it: big needs come from the coldest tier, everyday spending from the hot one. The payoff is that you’re never afraid to touch your savings, because you haven’t mixed them with your spending money.

The arrangements people reach for instead, and where each one goes wrong. None of them is stupid; each is a reasonable idea that runs into the same distinction above.

• One wallet for everything, kept cold. Safe, and it quietly stops you using Bitcoin — which matters more than it sounds, because a wallet you are reluctant to touch is a wallet you stop rehearsing, and an untested backup is the failure this course keeps coming back to.
• One wallet for everything, kept hot. The balance climbs a little at a time and there is no day on which it obviously becomes savings. That is the whole risk: nobody decides to keep their savings on a phone, they just never move them off it.
• A phone wallet for savings, because it is non-custodial. These are two different questions and it is easy to answer the wrong one. Non-custodial is about who holds the keys, and a phone wallet passes — they are genuinely yours. Hot and cold is about what can reach them, and there it fails. Both things are true at once.
• An old phone or laptop kept offline as a “cold wallet.” It is a general-purpose computer with radios, a browser and an update it will eventually want — it goes online again sooner or later, and it has no small trustworthy screen of its own to confirm an address on.
• A paper wallet — a single key printed out. Genuinely cold, and retired practice for good reasons: it is usually printed by a computer, it has no recovery standard behind it, and spending from one safely is a procedure most people get wrong the first time.

Match the effort to the amount. A phone wallet is fine for spending money — but the moment any of it is savings, it belongs cold, however small. At that point add a hardware wallet and keep only spending money on the phone. You may also hear people insist on strict air-gapping — a device that never plugs in and communicates only by scanned QR codes. It’s the most isolated form of cold storage, but for most people a well-managed hardware wallet that plugs in by USB is already strong enough. The discipline you bring matters more than the air gap.