View-only cold wallet
Your cold wallet, at a glance. Your keys, never online.
Coldkey shows Bitcoin and Ethereum balances, portfolio history and activity for wallets whose keys live on a USB stick. The site reads public addresses only — it cannot sign, send or move funds.
Free · No ads, no trackers · Works with Chrome and Edge for USB auto-lock
How it works
Three steps. No browser extension, no seed phrase typed into a website, ever.
Keep your keys on a USB stick
Your recovery phrase and private keys stay on the stick, offline. A small wallet.json file next to them lists only your public addresses.
Sign in and connect the USB
Press Connect USB and pick the drive. Your browser reads wallet.json locally and hands the site nothing but public addresses.
See everything — until you unplug
Balances, value over time, allocation, activity and receive QR codes. Remove the stick and the portfolio locks within seconds.
Built to know as little as possible
Coldkey is a viewer, not a custodian. Here is exactly what it does and doesn't do.
- ✓Private keys never leave the USB. The site has no upload, field or API for keys or seed phrases.
- ✓Public addresses only. They are used to query blockchain data and are not stored on the server.
- ✓Auto-lock. The wallet file is re-checked every few seconds; unplugging the stick locks the session.
- ✓HTTPS with HSTS, strict Content-Security-Policy, scrypt-hashed passwords, rate-limited sign-in.
- ✓No ads, no analytics, no third-party scripts. Fonts are the only external asset.
- ✕Cannot send, swap or sign. There is no transaction feature — by design.
- ✕Not an exchange or custodian. Coldkey never holds funds.
- ✕Not financial advice. Prices and history come from public data providers and may be delayed.
- ✕Not a recovery service. If you lose the USB and your written recovery phrase, Coldkey cannot help — it never had them.
Data sources: Blockstream & mempool.space (Bitcoin), public Ethereum RPC nodes & Ethplorer (Ethereum), CoinGecko (prices). Read the security overview.
What you see
Portfolio value over time
1D · 1W · 1M · 1Y chart of your holdings valued at market prices, with allocation and 24h / period change.
Activity
Received and sent transactions per address, with confirmations and one-click links to block explorers.
Receive with QR
Share an address or QR code to receive coins. Verify the first and last characters before sending.
Live markets
Top coins by market cap with 1h / 24h / 7d changes and sparklines — open markets, no account needed.
Hide balances
One click masks every amount on screen for when you are not alone.
Eject any time
Lock the portfolio manually, or just pull the USB stick.
Questions
Does Coldkey ever see my private key or recovery phrase?
No. There is no way to enter one. The only file the site reads is wallet.json, which contains public addresses. Keep the key file on the USB only.
Which coins are supported?
Bitcoin (BTC) and Ethereum (ETH) including ERC-20 token balances on the same address. More chains may be added later.
Which browsers work?
Any modern browser can open wallet.json as a file. The Connect USB button with automatic lock on removal uses the File System Access API, available in Chrome and Edge.
What do you store about me?
A username, a salted password hash and a session cookie. Public addresses are used to fetch balances and are not stored. See the privacy policy.
Is this free?
Yes. There are no fees, subscriptions or ads.