What is hot wallet?

A wallet whose private keys are stored on an internet-connected device such as a phone or browser extension.

Hot wallets are convenient for frequent use but more exposed to malware and phishing. Contrast with cold wallet.

Nearly everyone starts here, because a hot wallet is free, installs in a minute, and is the only practical way to interact with applications on chain. The useful framing is not hot versus cold as a moral choice, but how much value belongs on a device that also runs a browser. Exchanges make the same split internally, keeping a small operating balance hot and the bulk in cold storage.

How it works

The defining property is that the signing key exists in memory or storage on a device connected to the internet. When you approve a transaction, the wallet software signs it locally and broadcasts it. There is no second device to confirm what you approved and no air gap between the key and whatever else is running on the machine.

That produces a specific threat model. Malware that reads browser storage or memory can extract the key or the encrypted vault plus the keystrokes that unlock it. Clipboard-replacing malware swaps a pasted destination address for the attacker's. A phishing site that imitates a wallet interface can collect a recovery phrase directly. And a malicious contract can request a token approval that grants unlimited spending, which is not a key theft at all but produces the same result.

The mitigations are ordinary and effective. Keep the balance small and treat it as spending money. Use a separate browser profile, or a separate device, for anything holding value. Revoke token approvals you no longer use. Verify the destination address on screen after pasting, not before. And keep the recovery phrase off the machine entirely, since a phrase stored in a password manager on the same computer inherits that computer's exposure.

Example

Illustrative allocation. You hold $6,000 of crypto. You keep $300 in a browser wallet for on-chain activity and $5,700 on a hardware device. A drainer site tricks you into approving a malicious transaction from the browser wallet. The worst case is $300 plus whatever tokens that wallet had approved elsewhere. Had the full $6,000 been in one hot wallet, the same single click would have taken all of it. The security difference was not the software. It was the split.

Why it matters when you buy

A purchase leaves you with a custody decision: leave it on the exchange, move it to a hot wallet, or move it to cold storage. Withdrawal costs differ by venue and network, so check the fee comparison before choosing a route, and the chain pages show which networks are cheap to move on. The first crypto wallet guide covers setup, and address poisoning and clipboard attacks covers the most common theft at withdrawal time.

Related terms

• cold wallet: keys kept on an offline device
• hardware wallet: the usual cold option for individuals
• token approval: the permission drainers abuse
• wallet drainer: the malicious contract behind most losses
• phishing: how access is usually obtained
• clipboard malware: address swapping at paste time

Questions

Is a hot wallet safe enough for small amounts?

For amounts you would be annoyed but not harmed to lose, yes, and that is the standard practice. Size the balance to what a single bad click could cost you.

Is a mobile wallet safer than a browser extension?

Mobile operating systems isolate apps more strictly, which helps, but the phone is still online and the same phishing and approval attacks work. The difference is smaller than it sounds.

Is money on an exchange a hot wallet?

Not yours. The exchange holds the keys, splitting balances between hot and cold storage of its own, and your claim is an account balance rather than a key you control.