The short version: you can see every coin in your cold storage from your phone without any key material ever leaving the safe. It takes five minutes to set up, it removes the main reason people handle their seed unnecessarily — and it quietly tells a stranger's server every address you own unless you configure it carefully.

Tuga sleeps in the hanging chair and I check on her from the kitchen window. I can see whether she's there, how she's lying, whether she's breathing in that flat-out way that means she's properly asleep rather than pretending.

What I don't do is go out and pick her up to confirm she's fine. That would tell me nothing I can't already see and it would ruin the thing I was checking on.

Most people have no equivalent for their bitcoin. They want to know it's still there, and the only tool they're confident using is the one that involves plugging in a device and entering a PIN. So they handle the hardware wallet to answer a question that didn't require handling anything — and handling is when mistakes happen.

1. What a watch-only wallet is

When you set up a wallet, the seed generates a hierarchy of keys. From it you can derive an extended public key — an xpub (or zpub, depending on address type) — which can produce every receiving address your wallet will ever use, and can verify balances against the chain.

What it cannot do is spend. It contains no private keys. There is no sequence of operations, no bug, no malware, no amount of cleverness that turns an xpub into the ability to move coins.

So you can export it from your hardware wallet, import it into a wallet app on your laptop or phone, and have a complete, live, accurate view of your holdings — on a device you'd never trust with the real thing.

2. Why this matters more than it sounds

It removes the reason to touch your cold storage. Every time you plug in the device, enter the PIN, and navigate the app, you're exposing yourself to a small chance of error, observation or a compromised machine. Doing that out of anxiety rather than need is pure downside. A watch-only wallet answers the anxiety for free.

It lets you verify receipts instantly. Someone paid you; you can confirm it arrived without producing the keys.

It gives you a working inventory. Which wallet holds what, across however many you've accumulated, in one view. This is the operational half of the bookkeeping article.

It's the safe way to let someone else see. A partner can have the watch-only wallet on their phone — full visibility, zero ability to spend, zero risk if the phone is lost. For couples where one person manages this and the other is uneasy about it, this is often the thing that resolves the discomfort.

And it's how you build a transaction safely. The watch-only wallet constructs an unsigned transaction; the signing happens on the air-gapped device. That's the PSBT flow I wrote about — and the watch-only wallet is its front half.

3. Setting it up

Export the xpub from the hardware wallet, usually via its companion app or by showing a QR code. Make sure you take the one matching your address type — the wallet names this, and picking wrong gives you a correct-looking wallet with no transactions in it, which panics people unnecessarily.

Import it into Sparrow, Electrum, BlueWallet, or your wallet of choice, as a watch-only or "public key only" wallet.

Verify it matches. Compare the first receiving address shown against one your hardware wallet displays on its own screen. If they match, you've imported the right thing.

Label it clearly so that future-you knows which device this corresponds to.

That's it. No key material has moved.

4. The privacy problem, which is the real catch

Here's what the setup guides tend to skip.

A watch-only wallet has to ask someone for your balance. By default, most wallets ask a public server — and in doing so they hand over every address derived from your xpub, all at once, linked together, to an operator you've never heard of, along with your IP address.

That's a complete map of your holdings, delivered voluntarily. It doesn't let them spend anything. It does mean a stranger knows exactly what you own, when you received it, and roughly where you are.

Three ways out, in order of effort:

Connect it to your own node. The clean answer. Your wallet queries your own machine and nobody else is involved. If you already run one, this is a settings change.

Use Tor. Most good wallets support it. The server still learns your addresses but not your network location.

Pick your server deliberately. If you're going to use someone else's, at least know whose, rather than accepting whatever default shipped.

If you do none of these, a watch-only wallet is still safer than handling your seed — you've traded a spending risk for a privacy cost. Just make the trade knowingly rather than by default.

5. The uncomfortable half

An xpub leaked is permanent and total. It can't spend, so people treat it as harmless and paste it into portfolio trackers, tax tools, spreadsheets and support chats. Anyone holding it sees every address you will ever generate from that wallet — past, present and future — and can watch your balance forever. You cannot revoke it. The only remedy is moving everything to a new wallet. Treat an xpub as read-only and radioactive, not as public.

The convenience invites worse habits. Having an easy balance view encourages checking it, and checking it frequently is behaviourally corrosive for the long-term holder — the whole argument of my piece on the behaviour gap. I'd rather you checked a watch-only wallet than your seed, but I'd rather again that you checked neither.

And it still doesn't prove you can spend. This is the trap. A healthy balance on screen says the coins exist at addresses derived from that xpub. It says nothing about whether your seed backup is correct, whether you recorded the passphrase, or whether the restore would work. People see a reassuring number and conclude their setup is sound. The number and the recoverability are completely independent, and only one of them is on your screen.

I can see her from the kitchen and I don't need to go out there. Knowing something is fine and being able to do something about it are separate; make sure you've tested the second one too. 🐾⚡