Inputs

An input says which coin you are spending. It doesn’t hold the coin or its value. It just points at an output of an earlier transaction, the way a cheque names an account.

Each input is 41 bytes: a pointer, an empty field and a sequence number. The signature that proves you may spend the coin isn’t in the input at all. It travels in the witness, matched to the input by position.

Try it

Pick the two-input example and hover each input’s fields.

What’s in an input?

Here is the one input of a real payment from block 130,825, highlighted:

A typical payment: 1 input, 2 outputs 205 bytes Copy

01000000 00 01 01 5939557091bae792be66f26cbd83fc78f16a690a854109e8a1d115e253812133 ab020000 00 ffffffff 02 b0359f1100000000 22 5120d7ab02c96a342bdddb5d07b9f3ebd6c04e077ff41418110b9a1e5997439416b2 00c2eb0b00000000 22 512062e9da3682aab288392cf7218bafc36287288abb3ce200c5d1a50aa234073b2b 01 40 4686c7014749649b25555874c7772ecb7a44e85454893ed5888db11ebcdc82a22d74ce1a1671d02810f5ba1dca3277409e95a653ba9644099f7da26be7a86ba2 00000000

Hover or focus the bytes to name each field Version bytes 0–3 1 Marker bytes 4 0x00 Flag bytes 5 0x01 Input count bytes 6 1 Previous txid bytes 7–38 33218153e215d1a1e80941850a696af178fc83bd6cf266be92e7ba9170553959 Output index bytes 39–42 683 scriptSig length bytes 43 0 Sequence bytes 44–47 0xffffffff Output count bytes 48 2 Amount bytes 49–56 295,646,640 grains (2.95646640 PRL) Script length bytes 57 34 Locking script bytes 58–91 prl1p674s9jt2xs4amk6aq7ul867kcp8qwll5zsvpzzu6revewsu5z6eqv9d5z4 Amount bytes 92–99 200,000,000 grains (2.00000000 PRL) Script length bytes 100 34 Locking script bytes 101–134 prl1pvt5a5d5z42egswfv7uscht7rv2rj3z4m8n3qp3w35592ydq88v4seuhn70 Witness items bytes 135 1 Schnorr signature length bytes 136 64 Schnorr signature bytes 137–200 4686c7014749649b25555874c7772ecb7a44e85454893ed5888db11ebcdc82a22d74ce1a1671d02810f5ba1dca3277409e95a653ba9644099f7da26be7a86ba2 Locktime bytes 201–204 0

Field	Bytes	Value
Version version	4 @0	1 int32 little-endian. Pearl wallets and pearld coinbases use version 1; relay policy accepts 1-2.
Marker marker	1 @4	0x00 Segwit marker (BIP-144): says witness data follows the outputs.
Flag flag	1 @5	0x01 Witness flag; 0x01 is the only value Pearl accepts.
Input count vin.length	1 @6	1 CompactSize number of inputs.
Previous txid vin[0].txid	32 @7	33218153e215d1a1e80941850a696af178fc83bd6cf266be92e7ba9170553959 The transaction being spent, stored byte-reversed (internal order); shown here in normal display order.
Output index vin[0].vout	4 @39	683 Which output of that transaction is spent (uint32 LE).
scriptSig length vin[0].scriptSig.length	1 @43	0 Always 0 for non-coinbase inputs in Pearl: every spend uses the witness instead.
Sequence vin[0].sequence	4 @44	0xffffffff Final (0xffffffff): no RBF signal, no relative locktime, and locktime is ignored for this input. Pearl wallets use this.
Output count vout.length	1 @48	2 CompactSize number of outputs.
Amount vout[0].value	8 @49	295,646,640 grains (2.95646640 PRL) int64 little-endian, in grains (1 PRL = 100,000,000 grains).
Script length vout[0].scriptPubKey.length	1 @57	34 CompactSize length of the locking script.
Locking script vout[0].scriptPubKey	34 @58	prl1p674s9jt2xs4amk6aq7ul867kcp8qwll5zsvpzzu6revewsu5z6eqv9d5z4 OP_1 OP_PUSHBYTES_32 <output key Q>: a Taproot output.
Amount vout[1].value	8 @92	200,000,000 grains (2.00000000 PRL) int64 little-endian, in grains (1 PRL = 100,000,000 grains).
Script length vout[1].scriptPubKey.length	1 @100	34 CompactSize length of the locking script.
Locking script vout[1].scriptPubKey	34 @101	prl1pvt5a5d5z42egswfv7uscht7rv2rj3z4m8n3qp3w35592ydq88v4seuhn70 OP_1 OP_PUSHBYTES_32 <output key Q>: a Taproot output.
Witness items witness[0].length	1 @135	1 Number of witness stack items for input 0.
Schnorr signature length witness[0][0].length	1 @136	64 CompactSize length of this witness item.
Schnorr signature witness[0][0]	64 @137	4686c7014749649b25555874c7772ecb7a44e85454893ed5888db11ebcdc82a22d74ce1a1671d02810f5ba1dca3277409e95a653ba9644099f7da26be7a86ba2 64-byte BIP-340 signature (R.x ‖ s) with SIGHASH_DEFAULT: a Taproot key-path spend.
Locktime locktime	4 @201	0 0: no time lock.

txid

d919e02a4adfd739ceef31d98803f0ddd24e1b1fa67b0fe572cdec42c1b384c9

Size

205 bytes · 154 vbytes

Block

130,825

Fee

7,915 grains

Previous txid

Size

32 bytes

Type

SHA256d hash

Format

Internal byte order (reversed from how explorers show it)

The bytes start 5939557091bae792…. Explorers show transaction IDs with their bytes reversed, so this is the transaction 33218153e215d1a1e80941850a696af178fc83bd6cf266be92e7ba9170553959. The txid page explains why the two orders exist.

Output index (vout)

Size

4 bytes

Type

Unsigned integer

Format

Little-endian

ab020000 is 0x2ab = 683. So the earlier transaction had at least 684 outputs, and this input spends number 683. The txid and index together are an outpoint: a unique name for one output, written 33218153…553959:683.

scriptSig

Size

1 byte (the length, 00)

Type

Script

Format

Empty

In Bitcoin’s original design, the scriptSig held the signature and public key. On Pearl it’s always empty, for a simple reason: every output you can spend is a witness program (Taproot or P2MR), and Pearl’s script engine refuses a non-empty scriptSig on those (“native witness program cannot also have a signature script”). The only scriptSig with content is a coinbase’s.

Sequence

Size

4 bytes

Type

Unsigned integer

Format

Little-endian

ffffffff, the maximum, which Pearl wallets always use: no replace-by-fee, no relative lock. Other values have meanings explained in locktime and sequence.

What doesn’t an input say?

Two important things: how much the coin is worth, and how it’s locked.

Every node already knows both. It keeps a table of every unspent output, the UTXO set, and looks up the outpoint there. For the payment above, the lookup says output 33218153…:683 holds 495,654,555 grains locked to prl1pfvyle3p7penvnezpg9awpa03ylfl0n30z3usygzvf8kt77wyra8suvzxy2.

Leaving them out saves space, but it means a signer has to trust whoever tells them the amounts. Taproot fixes that: the signed message includes every spent amount and locking script (see sighash), so a signer who’s lied to produces a signature that’s simply invalid.

What happens with several inputs?

They are listed one after another, after a count. This payment from block 130,822 has two, each spending output 0 of a different transaction:

2 inputs, 2 outputs 312 bytes Copy

01000000 00 01 02 207decc85aaf210383704c39294c193864bf8e4255984abab5fe19a891ea0fc5 00000000 00 ffffffff d5da316cc9db4a367ce18ef27fb76809601a7fde2d111844962fc7584fceadf7 00000000 00 ffffffff 02 782d7c0700000000 22 51206f03b8c53fff74f0b22844a62fb29f822fda5f4e062d492f1d91bf567361a340 c07fdc0b00000000 22 5120e407fefe99e7ae5957da27b1565b4c9568fcd0a7c1b01ee8b79e694f0ec52fbd 01 40 bcdee9e8c70a956f0faf3f19324ff7595aa9d6d377010f12a392d5dfb8a20b05076090f11d7d6523f995c316c40b5c4c635853491a29dd5367e54e899e460638 01 40 9c9a3f1689bc718d7cbf2639e1433e7bb0f01896c7f2c14a565d515c41a5b5cd0e4a748978492d8dbda559088b66ef79003d421098cc25ef4ab05b39256790b8 00000000

Hover or focus the bytes to name each field Version bytes 0–3 1 Marker bytes 4 0x00 Flag bytes 5 0x01 Input count bytes 6 2 Previous txid bytes 7–38 c50fea91a819feb5ba4a9855428ebf6438194c29394c70830321af5ac8ec7d20 Output index bytes 39–42 0 scriptSig length bytes 43 0 Sequence bytes 44–47 0xffffffff Previous txid bytes 48–79 f7adce4f58c72f964418112dde7f1a600968b77ff28ee17c364adbc96c31dad5 Output index bytes 80–83 0 scriptSig length bytes 84 0 Sequence bytes 85–88 0xffffffff Output count bytes 89 2 Amount bytes 90–97 125,578,616 grains (1.25578616 PRL) Script length bytes 98 34 Locking script bytes 99–132 prl1pdupm33flla60pv3ggjnzlv5lsgha5h6wqck5jtcajxl4vump5dqq3mvacr Amount bytes 133–140 199,000,000 grains (1.99000000 PRL) Script length bytes 141 34 Locking script bytes 142–175 prl1pusrlal5eu7h9j476y7c4vk6vj450e598cxcpa69hne557rk9977skn6lrw Witness items bytes 176 1 Schnorr signature length bytes 177 64 Schnorr signature bytes 178–241 bcdee9e8c70a956f0faf3f19324ff7595aa9d6d377010f12a392d5dfb8a20b05076090f11d7d6523f995c316c40b5c4c635853491a29dd5367e54e899e460638 Witness items bytes 242 1 Schnorr signature length bytes 243 64 Schnorr signature bytes 244–307 9c9a3f1689bc718d7cbf2639e1433e7bb0f01896c7f2c14a565d515c41a5b5cd0e4a748978492d8dbda559088b66ef79003d421098cc25ef4ab05b39256790b8 Locktime bytes 308–311 0

Field	Bytes	Value
Version version	4 @0	1 int32 little-endian. Pearl wallets and pearld coinbases use version 1; relay policy accepts 1-2.
Marker marker	1 @4	0x00 Segwit marker (BIP-144): says witness data follows the outputs.
Flag flag	1 @5	0x01 Witness flag; 0x01 is the only value Pearl accepts.
Input count vin.length	1 @6	2 CompactSize number of inputs.
Previous txid vin[0].txid	32 @7	c50fea91a819feb5ba4a9855428ebf6438194c29394c70830321af5ac8ec7d20 The transaction being spent, stored byte-reversed (internal order); shown here in normal display order.
Output index vin[0].vout	4 @39	0 Which output of that transaction is spent (uint32 LE).
scriptSig length vin[0].scriptSig.length	1 @43	0 Always 0 for non-coinbase inputs in Pearl: every spend uses the witness instead.
Sequence vin[0].sequence	4 @44	0xffffffff Final (0xffffffff): no RBF signal, no relative locktime, and locktime is ignored for this input. Pearl wallets use this.
Previous txid vin[1].txid	32 @48	f7adce4f58c72f964418112dde7f1a600968b77ff28ee17c364adbc96c31dad5 The transaction being spent, stored byte-reversed (internal order); shown here in normal display order.
Output index vin[1].vout	4 @80	0 Which output of that transaction is spent (uint32 LE).
scriptSig length vin[1].scriptSig.length	1 @84	0 Always 0 for non-coinbase inputs in Pearl: every spend uses the witness instead.
Sequence vin[1].sequence	4 @85	0xffffffff Final (0xffffffff): no RBF signal, no relative locktime, and locktime is ignored for this input. Pearl wallets use this.
Output count vout.length	1 @89	2 CompactSize number of outputs.
Amount vout[0].value	8 @90	125,578,616 grains (1.25578616 PRL) int64 little-endian, in grains (1 PRL = 100,000,000 grains).
Script length vout[0].scriptPubKey.length	1 @98	34 CompactSize length of the locking script.
Locking script vout[0].scriptPubKey	34 @99	prl1pdupm33flla60pv3ggjnzlv5lsgha5h6wqck5jtcajxl4vump5dqq3mvacr OP_1 OP_PUSHBYTES_32 <output key Q>: a Taproot output.
Amount vout[1].value	8 @133	199,000,000 grains (1.99000000 PRL) int64 little-endian, in grains (1 PRL = 100,000,000 grains).
Script length vout[1].scriptPubKey.length	1 @141	34 CompactSize length of the locking script.
Locking script vout[1].scriptPubKey	34 @142	prl1pusrlal5eu7h9j476y7c4vk6vj450e598cxcpa69hne557rk9977skn6lrw OP_1 OP_PUSHBYTES_32 <output key Q>: a Taproot output.
Witness items witness[0].length	1 @176	1 Number of witness stack items for input 0.
Schnorr signature length witness[0][0].length	1 @177	64 CompactSize length of this witness item.
Schnorr signature witness[0][0]	64 @178	bcdee9e8c70a956f0faf3f19324ff7595aa9d6d377010f12a392d5dfb8a20b05076090f11d7d6523f995c316c40b5c4c635853491a29dd5367e54e899e460638 64-byte BIP-340 signature (R.x ‖ s) with SIGHASH_DEFAULT: a Taproot key-path spend.
Witness items witness[1].length	1 @242	1 Number of witness stack items for input 1.
Schnorr signature length witness[1][0].length	1 @243	64 CompactSize length of this witness item.
Schnorr signature witness[1][0]	64 @244	9c9a3f1689bc718d7cbf2639e1433e7bb0f01896c7f2c14a565d515c41a5b5cd0e4a748978492d8dbda559088b66ef79003d421098cc25ef4ab05b39256790b8 64-byte BIP-340 signature (R.x ‖ s) with SIGHASH_DEFAULT: a Taproot key-path spend.
Locktime locktime	4 @308	0 0: no time lock.

txid

091166043c8d93530171ca9e5ac883aaeae467934fbb8e4df1ea739c8d71b23e

Size

312 bytes · 212 vbytes

Block

130,822

Fee

10,650 grains

The count byte is 02. In the witness, the first stack belongs to input 0 and the second to input 1. Each input carries its own signature, even if the same wallet owns both coins.

Inputs add up. This transaction spends 113,300,000 + 211,289,266 = 324,589,266 grains and creates outputs worth 324,578,616 grains. The difference, 10,650 grains, is the fee.

Does the order of inputs matter?

Yes, in two ways. The witness stacks follow the inputs in the same order, so the first stack proves the first input, and so on. And each signature commits to the index of the input it signs (see sighash), so moving a signature to another input breaks it.

Which coins to use, and in which order, is the wallet’s choice. Pearl’s wallet picks the largest coins first by default, then adds a change output at a random position. Spending several coins together tells the world they probably share an owner, one of the reasons wallets give out a fresh address for every payment.

What does a coinbase input look like?

The first transaction of every block creates new coins, so it has nothing to point at. Its single input uses a null outpoint, 32 zero bytes and index ffffffff, and its scriptSig starts with the block height:

Coinbase of block 130,825 216 bytes Copy

02000000 00 01 01 0000000000000000000000000000000000000000000000000000000000000000 ffffffff 27 0309ff01048393d76a2f706f6f6c2e6b7279707465782e636f6d2f1550cad31e016e7bf00f2ecb ffffffff 02 cc84ce1d34000000 22 5120e31e8032a67b9af27dc279f448c003457bae6c5d28de7ee719bc87b6801ede17 0000000000000000 26 6a24aa21a9ed78cc1a61dcfcee9c59ddd9f4d56a98764c071e077bcc36fe9d1cf0aad50ebac3 01 20 0000000000000000000000000000000000000000000000000000000000000000 00000000

Hover or focus the bytes to name each field Version bytes 0–3 2 Marker bytes 4 0x00 Flag bytes 5 0x01 Input count bytes 6 1 Previous txid bytes 7–38 0000000000000000000000000000000000000000000000000000000000000000 Output index bytes 39–42 0xffffffff scriptSig length bytes 43 39 Coinbase script bytes 44–82 0309ff01048393d76a2f706f6f6c2e6b7279707465782e636f6d2f1550cad31e016e7bf00f2ecb Sequence bytes 83–86 0xffffffff Output count bytes 87 2 Amount bytes 88–95 223,838,373,068 grains (2238.38373068 PRL) Script length bytes 96 34 Locking script bytes 97–130 prl1puv0gqv4x0wd0ylwz086y3sqrg4a6umza9r08aecehjrmdqq7mctsmqaqsh Amount bytes 131–138 0 grains (0.00000000 PRL) Script length bytes 139 38 Locking script bytes 140–177 witness commitment 78cc1a61dcfcee9c59ddd9f4d56a98764c071e077bcc36fe9d1cf0aad50ebac3 Witness items bytes 178 1 Witness reserved value length bytes 179 32 Witness reserved value bytes 180–211 0000000000000000000000000000000000000000000000000000000000000000 Locktime bytes 212–215 0

Field	Bytes	Value
Version version	4 @0	2 int32 little-endian. Pearl wallets and pearld coinbases use version 1; relay policy accepts 1-2.
Marker marker	1 @4	0x00 Segwit marker (BIP-144): says witness data follows the outputs.
Flag flag	1 @5	0x01 Witness flag; 0x01 is the only value Pearl accepts.
Input count vin.length	1 @6	1 CompactSize number of inputs.
Previous txid vin[0].txid	32 @7	0000000000000000000000000000000000000000000000000000000000000000 All zeros: this input creates new coins (coinbase).
Output index vin[0].vout	4 @39	0xffffffff 0xffffffff together with a zero txid marks a coinbase.
scriptSig length vin[0].scriptSig.length	1 @43	39 CompactSize length of the scriptSig.
Coinbase script vin[0].scriptSig	39 @44	0309ff01048393d76a2f706f6f6c2e6b7279707465782e636f6d2f1550cad31e016e7bf00f2ecb Coinbase data. It starts with the block height 130825 (BIP-34, required in every Pearl block), then anything the miner likes.
Sequence vin[0].sequence	4 @83	0xffffffff Final (0xffffffff): no RBF signal, no relative locktime, and locktime is ignored for this input. Pearl wallets use this.
Output count vout.length	1 @87	2 CompactSize number of outputs.
Amount vout[0].value	8 @88	223,838,373,068 grains (2238.38373068 PRL) int64 little-endian, in grains (1 PRL = 100,000,000 grains).
Script length vout[0].scriptPubKey.length	1 @96	34 CompactSize length of the locking script.
Locking script vout[0].scriptPubKey	34 @97	prl1puv0gqv4x0wd0ylwz086y3sqrg4a6umza9r08aecehjrmdqq7mctsmqaqsh OP_1 OP_PUSHBYTES_32 <output key Q>: a Taproot output.
Amount vout[1].value	8 @131	0 grains (0.00000000 PRL) int64 little-endian, in grains (1 PRL = 100,000,000 grains).
Script length vout[1].scriptPubKey.length	1 @139	38 CompactSize length of the locking script.
Locking script vout[1].scriptPubKey	38 @140	witness commitment 78cc1a61dcfcee9c59ddd9f4d56a98764c071e077bcc36fe9d1cf0aad50ebac3 OP_RETURN aa21a9ed ‖ SHA256d(witness Merkle root ‖ nonce): the BIP-141 witness commitment.
Witness items witness[0].length	1 @178	1 Number of witness stack items for input 0.
Witness reserved value length witness[0][0].length	1 @179	32 CompactSize length of this witness item.
Witness reserved value witness[0][0]	32 @180	0000000000000000000000000000000000000000000000000000000000000000 The coinbase witness is one 32-byte value (the witness-commitment nonce); pearld uses zeros.
Locktime locktime	4 @212	0 0: no time lock.

txid

0a2acb6004406b21252d1578585dec84efd7e7547f1bca19c30c17538c51caa0

Size

216 bytes · 189 vbytes

Block

130,825

That’s how nodes recognize a coinbase. The coinbase page decodes its scriptSig.

What rules does an input have to follow?

• The output must exist and be unspent. Spending the same outpoint twice is a double spend; only one of the two transactions can ever be in the chain.
• New coins must wait. An output from a coinbase can’t be spent until it is 100 blocks deep.
• Parents first. If an input spends an output created in the same block, the parent transaction must come earlier in the block. Pearl enforces this from v1.5.1.
• There must be a witness. Pearl’s mempool rejects a transaction with no witness data at all.