@abi.decode

Decode ABI-encoded bytes into values given a comma-separated type list; a lens selects one of them.

On-chain (@abi.decode!): Needs a [_ $] lens and returns only the selected value; the data argument must be a live call or bytes expression, and array selections are refused.

Returns: any

Syntax

@abi.decode(types data lens?)

Arguments

Name	Type	Description
types	string	Comma-separated Solidity types (e.g. "uint256,address")
data	bytes	ABI-encoded hex data
[lens]	array	A [_ $] lens selecting one decoded value; without it the whole decoded array is returned

Examples

# Decode a single uint256
set $values @abi.decode("uint256" 0x0000000000000000000000000000000000000000000000000000000000000064)
print $values

# Decode multiple types
set $values @abi.decode("uint256,address" 0x000000000000000000000000000000000000000000000000000000000000002a00000000000000000000000044fa8e6f47987339850636f88629646662444217)
print $values

On-chain face

@abi.decode! re-enters an encoded blob at judge time. The type list is the author's claim about the payload's encoding, exactly as a typed :: hop's inline ABI is: a wrong claim reverts loudly in almost all cases, but a shape-compatible wrong claim can read the wrong value. Two things tighten versus the off-chain face:

• A [_ $] lens is required. An on-chain expression yields one value, so the lens says which decoded value that is — the same $/_/... vocabulary a return lens uses, as a separate argument. Nested [ ] reach into structs; array selections are refused (select an element or a string/bytes value instead).
• data must be a live call or bytes expression — a :: call whose return lens picks a bytes field out of a multi-value return, or a nested bytes helper. A build-time constant has nothing to assert about; decode those with the off-chain face.

# The report blob encodes (address,uint256); judge its uint on-chain
assert @abi.decode!("address,uint256" 0xe91D153E0b41518A2Ce8Dd3D7944Fa863463a97d::{lastReport()(uint256,bytes)}[_ $] [_ $]) > 0

The payload is read in place: the compiled form appends the core's PAYLOAD sentinel to the navigation that reaches the bytes field, and the selection rides a second nav whose descriptor is the claimed type list — no copying, one extra frame. A string selected out of the payload composes with the string helpers like any other string value.

See Also

• @abi.encode — the inverse: ABI-encode values
• @abi.encodeCall — ABI-encode a function call
• @abi.encodePacked — packed encoding