Opcodes

Every Script opcode — value, operand, stack effect, and era status

This page is the reference for every Script word (opcode) recognised by the BSV protocol: its exact byte value, how many script bytes its operand occupies, its effect on the stack, and the protocol era in which it is enabled, disabled, or re-instated.

Ground truth. Every opcode value on this page derives from enum opcodetype in src/script/opcodes.h. Per-opcode stack behaviour and era gating derive from EvalScript in src/script/interpreter.cpp. All citations are pinned to release v1.2.2 (commit 879fc8b).

How to read this page

Every opcode table has the following columns:

Column	Meaning
Word	The opcode mnemonic. Where two names share a value (e.g. OP_0/OP_FALSE), both are given.
Decimal	The opcode's value in decimal.
Hex	The opcode's value as a single byte in hexadecimal.
Operand (bytes read)	How many additional script bytes the interpreter consumes from the script stream for this opcode's operand, and how the length is encoded. This concerns only the leading push opcodes; for every other opcode it is none (the opcode is a single byte and takes all its arguments from the stack, not the script).
Input	Stack items consumed, top of stack rightmost. An item annotated (num) is interpreted as a number, not a raw byte array — see Numeric arguments for the encoding and size rules.
Output	Stack items produced, top of stack rightmost.
Description	Precise behaviour, including failure conditions.
Status by era	Whether the opcode is enabled, disabled, or a no-op in each protocol era (see Protocol eras).

Truth values. False is a zero-length array, a value that is all zero bytes, or a value that is zero bytes followed by a sign byte of 0x80 (negative zero). True is anything else.

Numeric arguments

Wherever a stack item is consumed as a number (marked (num) in the Input column — e.g. the shift count of OP_LSHIFTNUM, the position of OP_SPLIT, the start/length of OP_SUBSTR, or the operands of the arithmetic opcodes) it is decoded as a CScriptNum (src/script/script_num.h):

• Encoding: little-endian, sign-magnitude — the most-significant bit of the last byte is the sign, so the value is negative when that bit is set.
• Minimal encoding: when minimal-data enforcement is active, a number must use the fewest possible bytes (no redundant trailing 0x00/0x80), otherwise the script fails. From Chronicle, transactions with version > 1 may opt out of this check (see Script).
• Maximum length of the serialized number, by era (MaxScriptNumLength, src/consensus/consensus.h): 4 bytes Pre-Genesis (range [−2³¹+1, 2³¹−1]), 750,000 bytes Genesis, 32 MB Chronicle. A number longer than the era limit is rejected.
• Integer domain: when a number is used as a machine integer (e.g. a length or index, via getint/getint64) it must fit in a signed 64-bit integer (INT64_SERIALIZED_SIZE = 9 bytes on the wire, including the sign byte); a value outside that domain, or one that fails an opcode's own range test, fails the script with SCRIPT_ERR_INVALID_NUMBER_RANGE.

Stack items that are not marked (num) (e.g. the source string of OP_SUBSTR, the inputs to OP_CAT, a signature or public key) are treated as raw byte arrays and are not subject to the numeric-length limit above — only to the element/ stack-memory limits described in Script.

Protocol eras

The interpreter recognises three eras, selected per input from the era in force when the spent UTXO was confirmed (the "UTXO height" rule; the Protocol Upgrade History page will catalogue the activation heights):

Era	Mainnet activation	Meaning
Pre-Genesis	before block 620,538	Original rules with the 2017–2018 upgrades applied.
Genesis	height ≥ 620,538	Genesis upgrade (2020-02-04).
Chronicle	height ≥ 943,816	Chronicle upgrade (2026-04-07).

In the source these correspond to ProtocolEra::PreGenesis, PostGenesis, and PostChronicle, resolved from the script flags at the top of EvalScript.

Constants (push opcodes)

These value-pushing words place data onto the stack. They are the only opcodes that read operand bytes from the script; see Push-data operands for the byte-exact encoding.

Word	Decimal	Hex	Operand (bytes read)	Input	Output	Description	Status by era
OP_0, OP_FALSE	0	0x00	none	—	(empty)	Pushes an empty byte array. Not a no-op: an item is added to the stack.	All
(direct push)	1–75	0x01–0x4b	the operand is the next N bytes, where N = the opcode value	—	data	Push the next opcode-value bytes as one stack item. No separate length field.	All
OP_PUSHDATA1	76	0x4c	1 length byte, then that many data bytes	—	data	Next 1 byte is the length; then that many data bytes are pushed.	All
OP_PUSHDATA2	77	0x4d	2 length bytes (LE), then data	—	data	Next 2 bytes little-endian are the length; then that many data bytes are pushed.	All
OP_PUSHDATA4	78	0x4e	4 length bytes (LE), then data	—	data	Next 4 bytes little-endian are the length; then that many data bytes are pushed.	All
OP_1NEGATE	79	0x4f	none	—	-1	Pushes the number −1.	All
OP_1, OP_TRUE	81	0x51	none	—	1	Pushes the number 1.	All
OP_2–OP_16	82–96	0x52–0x60	none	—	2–16	Pushes the number named in the word (2–16).	All

(source: opcodes.h L13–L36; push decode: script.h GetOp2 L163)

Flow control

Word	Decimal	Hex	Operand	Input	Output	Description	Status by era
OP_NOP	97	0x61	none	—	—	Does nothing.	All
OP_VER	98	0x62	none	—	tx version	Pushes the spending transaction's version (4-byte LE) onto the stack.	Pre-Genesis / Genesis: invalid (SCRIPT_ERR_BAD_OPCODE). Chronicle: enabled.
OP_IF	99	0x63	none	value	—	If the top value is true, the following branch executes. The top value is removed. Must be closed by OP_ENDIF.	All
OP_NOTIF	100	0x64	none	value	—	If the top value is false, the following branch executes. The top value is removed. Must be closed by OP_ENDIF.	All
OP_VERIF	101	0x65	none	value	—	Chronicle: as OP_IF but the condition is "top item equals the tx version (4-byte LE)".	Pre-Genesis / Genesis: invalid if executed (SCRIPT_ERR_BAD_OPCODE). Chronicle: enabled.
OP_VERNOTIF	102	0x66	none	value	—	Chronicle: negated OP_VERIF.	Pre-Genesis / Genesis: invalid if executed. Chronicle: enabled.
OP_ELSE	103	0x67	none	—	—	Executes if the matching OP_IF/OP_NOTIF branch did not.	All
OP_ENDIF	104	0x68	none	—	—	Ends an OP_IF/OP_NOTIF/OP_ELSE block. An unbalanced conditional makes the script invalid.	All
OP_VERIFY	105	0x69	none	value	— / fail	Fails the script if the top value is not true; otherwise removes it.	All
OP_RETURN	106	0x6a	none	—	terminates	See OP_RETURN semantics.	Pre-Genesis: fails the script (SCRIPT_ERR_OP_RETURN). Genesis / Chronicle: terminates evaluation; at top level the script succeeds and remaining bytes are ignored.

(source: opcodes.h L39–L48; gating: interpreter.cpp EvalScript)

Stack

Word	Decimal	Hex	Operand	Input	Output	Description	Status by era
OP_TOALTSTACK	107	0x6b	none	x1	(alt) x1	Moves the top item to the alt stack.	All
OP_FROMALTSTACK	108	0x6c	none	(alt) x1	x1	Moves the top alt-stack item to the main stack.	All
OP_2DROP	109	0x6d	none	x1 x2	—	Removes the top two items.	All
OP_2DUP	110	0x6e	none	x1 x2	x1 x2 x1 x2	Duplicates the top two items.	All
OP_3DUP	111	0x6f	none	x1 x2 x3	x1 x2 x3 x1 x2 x3	Duplicates the top three items.	All
OP_2OVER	112	0x70	none	x1 x2 x3 x4	x1 x2 x3 x4 x1 x2	Copies the pair two back to the top.	All
OP_2ROT	113	0x71	none	x1 x2 x3 x4 x5 x6	x3 x4 x5 x6 x1 x2	Moves the fifth/sixth items to the top.	All
OP_2SWAP	114	0x72	none	x1 x2 x3 x4	x3 x4 x1 x2	Swaps the top two pairs.	All
OP_IFDUP	115	0x73	none	x	x / x x	Duplicates the top item if it is not zero.	All
OP_DEPTH	116	0x74	none	—	<stack size> (num)	Pushes the current stack depth as a number.	All
OP_DROP	117	0x75	none	x	—	Removes the top item.	All
OP_DUP	118	0x76	none	x	x x	Duplicates the top item.	All
OP_NIP	119	0x77	none	x1 x2	x2	Removes the second-from-top item.	All
OP_OVER	120	0x78	none	x1 x2	x1 x2 x1	Copies the second-from-top item to the top.	All
OP_PICK	121	0x79	none	xn … x1 x0 <n> (num)	xn … x1 x0 xn	Copies the item n back to the top. Fails if n is negative or ≥ the stack depth.	All
OP_ROLL	122	0x7a	none	xn … x1 x0 <n> (num)	… x1 x0 xn	Moves the item n back to the top. Fails if n is negative or ≥ the stack depth.	All
OP_ROT	123	0x7b	none	x1 x2 x3	x2 x3 x1	Rotates the top three items left.	All
OP_SWAP	124	0x7c	none	x1 x2	x2 x1	Swaps the top two items.	All
OP_TUCK	125	0x7d	none	x1 x2	x2 x1 x2	Copies the top item behind the second item.	All

(source: opcodes.h L51–L69)

Data manipulation

Word	Decimal	Hex	Operand	Input	Output	Description	Status by era
OP_CAT	126	0x7e	none	x1 x2	out	Concatenates byte arrays x1 and x2. Pre-Genesis the result must be ≤ 520 bytes (else SCRIPT_ERR_PUSH_SIZE).	Enabled from May 2018.
OP_SPLIT	127	0x7f	none	x n (num)	x1 x2	Splits byte array x into x1 = x[0:n] and x2 = x[n:]. Fails (SCRIPT_ERR_INVALID_SPLIT_RANGE) if n < 0 or n > len(x).	Enabled from May 2018.
OP_NUM2BIN	128	0x80	none	a (num) b (num)	out	Encodes numeric value a as a byte array of length b. Fails (SCRIPT_ERR_IMPOSSIBLE_ENCODING) if a does not fit in b bytes; Pre-Genesis b must also be ≤ 520 (SCRIPT_ERR_PUSH_SIZE).	Enabled from May 2018.
OP_BIN2NUM	129	0x81	none	x	out (num)	Minimally re-encodes byte array x as a number. Fails if the result exceeds the era's max script-number length.	Enabled from May 2018.
OP_SIZE	130	0x82	none	in	in size (num)	Pushes the byte length of the top item (as a number) without removing it.	All

(source: opcodes.h L72–L76. The May-2018 re-enable date is historical, sourced from the consensus specs; the v1.2.2 interpreter applies no era gate to these opcodes.)

Bitwise logic

Word	Decimal	Hex	Operand	Input	Output	Description	Status by era
OP_INVERT	131	0x83	none	in	out	Flips every bit of the input.	Enabled from Nov 2018.
OP_AND	132	0x84	none	x1 x2	out	Bitwise AND. Operands must be equal length.	Enabled from May 2018.
OP_OR	133	0x85	none	x1 x2	out	Bitwise OR. Operands must be equal length.	Enabled from May 2018.
OP_XOR	134	0x86	none	x1 x2	out	Bitwise XOR. Operands must be equal length.	Enabled from May 2018.
OP_EQUAL	135	0x87	none	x1 x2	1 / 0	Pushes 1 if the two inputs are byte-identical, else 0.	All
OP_EQUALVERIFY	136	0x88	none	x1 x2	— / fail	As OP_EQUAL then OP_VERIFY.	All

(source: opcodes.h L79–L86)

Arithmetic

Arithmetic operates on numeric values (CScriptNum): little-endian, sign-magnitude (the high bit of the last byte is the sign), minimally encoded. Pre-Genesis a numeric operand must be ≤ 4 bytes (range [−2³¹+1, 2³¹−1]); from Genesis operands may be up to 750,000 bytes, and from Chronicle up to 32 MB. Byte sequences longer than the numeric-length limit are still valid script data but are not accepted as numbers. See Script for the number model.

Word	Decimal	Hex	Operand	Input	Output	Description	Status by era
OP_1ADD	139	0x8b	none	in (num)	out (num)	Adds 1.	All
OP_1SUB	140	0x8c	none	in (num)	out (num)	Subtracts 1.	All
OP_2MUL	141	0x8d	none	in (num)	out (num)	Multiplies by 2.	Disabled Pre-Genesis & Genesis (SCRIPT_ERR_DISABLED_OPCODE). Enabled at Chronicle.
OP_2DIV	142	0x8e	none	in (num)	out (num)	Divides by 2 (rounding toward zero).	Disabled Pre-Genesis & Genesis (SCRIPT_ERR_DISABLED_OPCODE). Enabled at Chronicle.
OP_NEGATE	143	0x8f	none	in (num)	out (num)	Flips the sign.	All
OP_ABS	144	0x90	none	in (num)	out (num)	Absolute value.	All
OP_NOT	145	0x91	none	in (num)	out (num)	1 → 0, 0 → 1, else 0.	All
OP_0NOTEQUAL	146	0x92	none	in (num)	out (num)	0 → 0, else 1.	All
OP_ADD	147	0x93	none	a (num) b (num)	out (num)	a + b.	All
OP_SUB	148	0x94	none	a (num) b (num)	out (num)	a − b.	All
OP_MUL	149	0x95	none	a (num) b (num)	out (num)	a × b.	Enabled from Nov 2018.
OP_DIV	150	0x96	none	a (num) b (num)	out (num)	a ÷ b. Fails on divisor 0 (SCRIPT_ERR_DIV_BY_ZERO).	Enabled from May 2018.
OP_MOD	151	0x97	none	a (num) b (num)	out (num)	Remainder of a ÷ b. Fails on divisor 0 (SCRIPT_ERR_MOD_BY_ZERO).	Enabled from May 2018.
OP_LSHIFT	152	0x98	none	a b (num)	out	Bit-string left shift: shifts the byte array a left by b bits (sign not interpreted). Fails (SCRIPT_ERR_INVALID_NUMBER_RANGE) if b < 0. Contrast OP_LSHIFTNUM, which treats a as a number.	Enabled from Nov 2018.
OP_RSHIFT	153	0x99	none	a b (num)	out	Bit-string right shift: shifts the byte array a right by b bits (sign not interpreted). Fails (SCRIPT_ERR_INVALID_NUMBER_RANGE) if b < 0. Contrast OP_RSHIFTNUM, which treats a as a number.	Enabled from Nov 2018.
OP_BOOLAND	154	0x9a	none	a (num) b (num)	out (num)	1 if both a and b are non-zero, else 0.	All
OP_BOOLOR	155	0x9b	none	a (num) b (num)	out (num)	1 if a or b is non-zero, else 0.	All
OP_NUMEQUAL	156	0x9c	none	a (num) b (num)	out (num)	1 if numerically equal, else 0.	All
OP_NUMEQUALVERIFY	157	0x9d	none	a (num) b (num)	— / fail	As OP_NUMEQUAL then OP_VERIFY.	All
OP_NUMNOTEQUAL	158	0x9e	none	a (num) b (num)	out (num)	1 if numerically unequal, else 0.	All
OP_LESSTHAN	159	0x9f	none	a (num) b (num)	out (num)	1 if a < b.	All
OP_GREATERTHAN	160	0xa0	none	a (num) b (num)	out (num)	1 if a > b.	All
OP_LESSTHANOREQUAL	161	0xa1	none	a (num) b (num)	out (num)	1 if a ≤ b.	All
OP_GREATERTHANOREQUAL	162	0xa2	none	a (num) b (num)	out (num)	1 if a ≥ b.	All
OP_MIN	163	0xa3	none	a (num) b (num)	out (num)	Smaller of a and b.	All
OP_MAX	164	0xa4	none	a (num) b (num)	out (num)	Larger of a and b.	All
OP_WITHIN	165	0xa5	none	x (num) min (num) max (num)	out (num)	1 if min ≤ x < max, else 0.	All

(source: opcodes.h L89–L118; OP_2MUL/OP_2DIV gating: interpreter.cpp IsOpcodeDisabled L360. Re-enable dates are historical, from the consensus specs.)

Cryptography

Word	Decimal	Hex	Operand	Input	Output