getBlockHeader

A builder function that returns the interaction to get a block header.

A block header contains metadata about a block without the full transaction details, making it more lightweight than fetching the entire block. This is useful when you only need block metadata like timestamp, height, parent hash, etc.

Use with 'fcl.atBlockId()' and 'fcl.atBlockHeight()' when building the interaction to get headers for specific blocks.

Import

You can import the entire package and access the function:

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import * as fcl from '@onflow/fcl';

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fcl.getBlockHeader(isSealed);

Or import directly the specific function:

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import { getBlockHeader } from '@onflow/fcl';

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getBlockHeader(isSealed);

Usage

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import * as fcl from '@onflow/fcl';

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// Get latest sealed block header

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const sealedHeader = await fcl

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.send([fcl.getBlockHeader(true)])

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.then(fcl.decode);

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console.log('Block height:', sealedHeader.height);

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console.log('Block timestamp:', sealedHeader.timestamp);

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console.log('Parent block ID:', sealedHeader.parentId);

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// Get header for specific block

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const blockHeader = await fcl

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.send([fcl.getBlockHeader(), fcl.atBlockHeight(12345)])

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.then(fcl.decode);

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// Get latest finalized block header

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const finalizedHeader = await fcl

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.send([fcl.getBlockHeader(false)])

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.then(fcl.decode);

Parameters

isSealed (optional)

• Type: boolean
• Description: Block finality state, true for sealed blocks, false for finalized blocks, null for latest

Returns

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export type InteractionBuilderFn = (

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ix: Interaction,

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) => Interaction | Promise<Interaction>;

A function that processes an interaction object

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