Reef — txbt4, BLAKE2b testnet4 · a node in this tabtestnet4 · test coins

Reef, a Bitcoin node and wallet in this tab

Overview

Balances
Available:… Pending:… Immature:… Total:…
The wallet is one key kept in this browser. Its balance comes from the tab's own validated copy of the chain: coins created since the snapshot at block 150,307. Pending is what is on its way to you, including change of payments not yet in a block.
Recent transactions

Send

Send Coins
Transaction Fee
Fee:
…A block comes about every 20 minutes; the lowest rate, 1 sat/vB, is enough today.
Every payment can be replaced with a higher fee, or cancelled, until a block takes it (the Transactions page).
Available: …
How a payment leaves this tabIt is built and signed here and checked by the same script rules the chain uses, then handed to relays (Nostr, kind 23503) where a node that serves txbt4 picks it up and broadcasts it. Until a block carries it, it shows as waiting and is announced again every 10 minutes, unless this tab's node refuses it.

Receive

Receive
The address of the one key this tab keeps. txbt4 only: coins sent to it on another testnet never arrive here. Test coins only; to get some, mine them in Winch or ask someone with a txbt4 node to send some. The same address is used every time.
scan to pay this tab (txbt4 only)
Coins held
Coins held by this wallet
BlockOutpointConfirmationsAmount (tBTC)
nothing received since the snapshot

Transactions

Transactions
DateStatusBlockTypeAddressAmount (tBTC)Actions
Loading…TESTNET4 · BLAKE2b one key in this tab (not HD, not encrypted): back it up from Settingsconnections
About Reef

Reef · a Bitcoin node in a browser tab, for txbt4, the BLAKE2b testnet4.

It looks like Knots and runs a chain Knots defined, but it is not Knots. The tab fetches the fork-point UTXO snapshot, recomputes its hashes, validates every block since the fork and follows the chain tip. The wallet is one key kept in this tab.

Source · Issues · blaketestnode · sidestr

Copyright © 2026 the Reef contributors. Licensed under the GNU Affero General Public License, version 3 or later.
Options
Wallet
Network
Display
the fork-point UTXO set: a plain file served with Range and CORS
the mirror's block file, given without its .dat
Storage in this tab:
…
the snapshot, its index and the block file live in the tab's private file system
…
sat/vB
Knots shows this as tBTC/kvB; 1 sat/vB is what txbt4 blocks take today
…
the notice in the page and the console line are always shown
Key:
…
the key is the wallet: whoever has it can spend the coins. It lives only in this browser until you back it up.
on OK you are asked to confirm; the current key is kept in the list below, but this browser is not a backup
Earlier keys:
none
a send is published as a kind 23503 event to each of these; a sidestr producer with a txbt4 node broadcasts it. The last publish: none yet
Blocks:
…
one mirror, read with Range requests; set on the Main tab
Chain tip:
wss://nos.lol · wss://relay.damus.io · wss://relay.nostr.band
the tab compares its chain with signed tip announcements from these (NIP-333); a mismatch or a tab far behind is shown at the top of the window
pieces come from whoever seeds the snapshot over WebRTC, and from the mirror; if the swarm gives nothing in a minute the tab fetches from the mirror alone. Takes effect on the next fetch: a first visit, or after Wipe.
the tab holds the checked file read-only and answers piece requests over WebRTC; upload shows on the Peers and Network Traffic tabs
also Settings → Mask values, or Alt+Shift+M
Windows:
Question
Back up the wallet key

The key is the wallet: anyone who has it can spend the coins, and if it is lost the coins are lost. It lives only in this browser; clearing site data, or the browser freeing space, removes it.

Keep a copy somewhere only you can read: a password manager, or the file below on another disk.

Address:
For other wallet softwareImport the descriptor (rawtr). The address is the key's own output, not a BIP 86 tr() address, so importing the WIF as tr() shows a different, empty address.

To restore: open Reef in any browser (Not now at the welcome is fine), then Settings → Options → Wallet → Use another key, and paste this key. The balance shows once the node runs and has checked the chain (a few minutes); coins received before block 150,307 are not shown by a tab.
Welcome to Reef

Reef is a Bitcoin node and wallet that runs in this tab, on txbt4, a test network (the BLAKE2b testnet4). Its coins are test coins with no value.

To start, the tab downloads the chain's state at block 150,307 (830 MB), checks it, and then validates every block since. That takes a few minutes on a fast connection (about 2 to 3 at 100 Mbit/s) and longer on a slow one; it is kept for next time, and resumes if interrupted. Avoid starting on a metered connection.

Nothing leaves the tab except requests for the chain and, when you pay, the signed payment. Your key is made here and stays in this browser: back it up. Not now still gives you an address; only the balance waits for the node.