Click a step to jump to it.

Value flow

bars are relative to the largest amount · click to jump

Transaction header

version · locktime · network · serialization

Header fields

Network

TX version

nLockTime 0x00000000

Locktime meaning

Serialization

PSBT version

Target fee rate sat/vB — used by "set fee"

Locktime date helper

Forensic controls

These unlock fields elsewhere in the workbench. Nothing here changes the transaction on its own — it changes what you are allowed to type. Turn on Forensic mode in the header to reveal the unlocked fields.

VALID — standard NON-STANDARD — consensus-valid, poorly relayed INVALID — consensus failure UNKNOWN — not enough information

At a glance

Quick start

Examples use regtest-style placeholder data. Switch the network freely — addresses re-encode.

Inputs

outpoints and the complete spending metadata each signer needs

Outputs

addresses, script templates, raw scripts and the OP_RETURN builder

Script Lab

build Bitcoin Script from opcodes, ASM or raw bytes — then send it anywhere in the transaction

Opcode palette

Insert data

Push value

Click any opcode to append it to the canvas. Drag canvas rows to reorder.

Script canvas

ASM ↔ HEX

ASM

HEX

Rendered

Derived

Send to…

Target input / output index

Signing Data

everything an external signer needs — and nothing that could sign here

Signer code — ready to run

Generated against the digests above. Fill in your own key, run it outside the browser, and paste the JSON it prints into Finalize → Signing JSON.

PSBT Lab

create, decode, compare and export BIP174 / BIP370 partially signed transactions

Generated PSBT

Base64

Hex

Bitcoin Core helper commands

Copy-paste into bitcoin-cli. The workbench deliberately holds no RPC credentials and makes no network calls.

Decode / import

Drop a .psbt file here, or click to choose

…or paste base64 / hex

Decoded structure

Nothing decoded yet.

Finalize

bring signatures back in, assemble scriptSig / witness, produce the broadcastable transaction

Import signed result

Signature status per input

Final transaction

Raw hex

Inspector

byte-by-byte decoding — hover any byte to see which field it belongs to

Byte-level view

Press Decode.

Field detail

Hover a byte.

Decoded

Structure

Validation

structural, consensus and relay-policy findings — reported, never enforced

Sighash commitment matrix

Raw Lab

the unrestricted bench: hashes, encodings, signature surgery, address conversion

Hash calculator

Input encoding

Tag BIP340 tagged hash

Data

Signature surgery

DER signature (with or without the sighash byte)

Build DER from r and s

r

s

Sighash byte

Result

Address ↔ script

Address

scriptPubKey hex

Byte utilities

Value

Result

Taproot bench

Internal key (x-only, 32 bytes)

Merkle root (optional)

Leaf script (hex)

Leaf version

Verify a signature

Public key (33 / 65 / 32 bytes)

Algorithm

Message digest z (32 bytes)

Signature

Toolkit

the supporting tools you reach for while building — descriptors, keys, trees, conversions, estimates

Output descriptors (BIP380)

Start from a pattern

Descriptor the checksum after # is computed for you

Extended key decoder (BIP32)

xpub / ypub / zpub / tpub / vpub …

Private keys are recognised but never displayed.

Taproot script tree builder

Internal key 32-byte x-only

Leaves script hex or ASM · leaf version defaults to 0xc0

Tree layout

—

Result

Units & number bases

Amount

Interpret as

Number base conversion

Value decimal, 0x hex, 0b binary, or bare hex

Locktime & sequence lab

nLockTime value

Current block height for the ETA

…or pick a date

nSequence — relative timelocks (BIP68)

Encode as

Value

Decode a raw value

Size & fee estimator

Inputs

Outputs

Fee rate (sat/vB)

Public key toolkit

Public key 33 / 65 / 32 bytes

Merkle root calculator

TXIDs, one per line display order, as you would read them in an explorer

Script analyser

Script hex

Multisig crafter

m-of-n from public keys — every variant computed live as you type

Public keys only. This builds the receiving side of a multisig wallet — the addresses and scripts. It never asks for, derives or stores a private key, so it cannot spend anything it creates.

Address

add a public key to begin

Every character of the address depends on every bit of every key.

Cosigner public keys

tick to include · drag order via the arrows

#Public key (33 / 65 / 32 bytes hex) StatusForm

Every variant of this key set

click a card to make it the headline address

Policy

2of3

Key order

Taproot options

Internal key x-only

NUMS removes the key path, so only the m-of-n script can spend.

Checks

What changed

Edit something to start the trail.

Use it

Descriptor

Target index

Node

optional live chain data over an Electrum WebSocket — off unless you connect it

DISCONNECTED

The workbench is fully usable offline. Connecting only adds chain lookups — fee estimates, UTXOs, previous transactions — and an explicitly confirmed broadcast. Private keys are never involved: there are none in this page to send.

Connection

One endpoint per chain, so switching networks switches servers. These are stored locally and never sent anywhere.

The port must be a WebSocket listener. A browser cannot open a plain TCP or SSL Electrum port, so Fulcrum's tcp = (usually 50001) and ssl = ports will not work here — you need ws = <port> (or wss =) in fulcrum.conf. One instance serves one chain; the genesis hash is checked on connect and a mismatch is reported rather than silently used.

Reconnect automatically when this page opens

UTXO lookup

Address or scriptPubKey hex

Fetch a transaction

TXID

Output index

Broadcast

Final transaction hex taken from Finalize; edit if you want to send something else

Chain

—: not connected

Fee estimates

Connect to load fee estimates.

Server banner

Traffic log

nothing yet