BCS

The @mysten/sui/bcs package extends @mysten/bcs with Sui specific scheme definitions.

To learn more about using BCS see the BCS documentation.

the bcs export of @mysten/sui/bcs contains all the same exports as bcs from @mysten/bcs plus the following pre-defined schemes:

• U8
• U16
• U32
• U64
• U128
• U256
• ULEB128
• Bool
• String
• Address
• Argument
• CallArg
• CompressedSignature
• GasData
• MultiSig
• MultiSigPkMap
• MultiSigPublicKey
• ObjectArg
• ObjectDigest
• ProgrammableMoveCall
• ProgrammableTransaction
• PublicKey
• SenderSignedData
• SharedObjectRef
• StructTag
• SuiObjectRef
• Transaction
• TransactionData
• TransactionDataV1
• TransactionExpiration
• TransactionKind
• TypeTag
• Object - Complete object with data, owner, previousTransaction, and storageRebate
• TransactionEffects - Transaction execution effects (supports both V1 and V2)
• TransactionEffectsV1 - Legacy transaction effects format
• TransactionEffectsV2 - Current transaction effects format with detailed object changes

All the upper-cased values are BcsType instances, and can be used directly to parse and serialize data.

import { bcs } from '@mysten/sui/bcs';

bcs.U8.serialize(1);
bcs.Address.serialize('0x1');
bcs.TypeTag.serialize({
	vector: {
		u8: true,
	},
});

Working with Objects

To parse on-chain objects, fetch them with include: { content: true } and pass object.content to a generated BCS type or a manual struct definition. The content field contains only the inner Move struct bytes:

import { MyStruct } from './generated/my-module';

const { object } = await client.core.getObject({
	objectId: '0x123...',
	include: { content: true },
});

const parsed = MyStruct.parse(object.content);

bcs.Object — Full object envelope

The bcs.Object schema represents the complete on-chain object, including metadata (type, owner, version, previous transaction, storage rebate) wrapping the inner struct bytes. This is what the objectBcs include option returns. Most of this metadata is already available as fields on the object response, so you typically only need content.

import { bcs } from '@mysten/sui/bcs';

// Parse a full object envelope (from objectBcs include option)
const envelope = bcs.Object.parse(object.objectBcs);
console.log('Owner:', envelope.owner);
console.log('Inner struct bytes:', envelope.data.Move.contents);

// Serialize a full object envelope
const serialized = bcs.Object.serialize({
	data: {
		Move: {
			type: { GasCoin: null },
			hasPublicTransfer: true,
			version: '1',
			contents: new Uint8Array([...]),
		},
	},
	owner: { AddressOwner: '0x...' },
	previousTransaction: '...',
	storageRebate: '1000',
});

Working with Transaction Effects

The bcs.TransactionEffects schema can be used to parse transaction effects:

import { bcs } from '@mysten/sui/bcs';

// Parse transaction effects
const effects = bcs.TransactionEffects.parse(effectsBytes);

// Check execution status
if (effects.V2.status.$kind === 'Success') {
	console.log('Transaction succeeded');
} else {
	console.log('Transaction failed:', effects.V2.status.Failure.error);
}

// Access changed objects
for (const [objectId, change] of effects.V2.changedObjects) {
	console.log('Object:', objectId);
	console.log('Output state:', change.outputState.$kind);
}