> ## Documentation Index
> Fetch the complete documentation index at: https://docs.metalntwx.com/llms.txt
> Use this file to discover all available pages before exploring further.

# Get a finality certificate

> Returns the retained Simplex finality certificate and block-header preimage for a finalized block hash. Nodes retain recent certificates, with a default limit of 100,000. Returns `null` when no certificate is retained or the corresponding header cannot be read, such as before finality, during local import, or after pruning.



## OpenAPI

````yaml /reference/json-rpc/json-rpc.json post /metal_getFinalityCertificate
openapi: 3.1.0
info:
  title: Metal JSON-RPC
  version: 1.0.0
  description: Interactive playground for Metal's public JSON-RPC endpoints.
servers:
  - url: https://rpc-testnet.metalntwx.com/v1/{endpointId}
    variables:
      endpointId:
        default: YOUR_ENDPOINT_ID
        description: >-
          Your endpoint ID from the Metal console. It is a credential, so keep
          it private. Paste it once, and the playground remembers it in this
          browser.
    description: Testnet
  - url: https://rpc-devnet.metalntwx.com
    description: Devnet
security: []
tags:
  - name: Chain
    description: Identify the chain and its head.
  - name: Consensus
    description: Simplex finality, node build, and gas-token metadata.
  - name: Blocks
    description: Read blocks with Metal's millisecond timestamps and proposer.
  - name: State
    description: Read accounts, contracts, and storage.
  - name: Gas
    description: Quote gas in MIP20 gas-token base units.
  - name: Transactions
    description: Submit and inspect transactions.
  - name: Logs
    description: Query event logs.
  - name: MIP20
    description: Gas-token pricing detail standard Ethereum responses cannot represent.
paths:
  /metal_getFinalityCertificate:
    post:
      tags:
        - Consensus
      summary: Get a finality certificate
      description: >-
        Returns the retained Simplex finality certificate and block-header
        preimage for a finalized block hash. Nodes retain recent certificates,
        with a default limit of 100,000. Returns `null` when no certificate is
        retained or the corresponding header cannot be read, such as before
        finality, during local import, or after pruning.
      operationId: metal_getFinalityCertificate
      requestBody:
        required: true
        content:
          application/json:
            schema:
              type: object
              required:
                - jsonrpc
                - id
                - method
                - params
              properties:
                jsonrpc:
                  type: string
                  enum:
                    - '2.0'
                  default: '2.0'
                  description: JSON-RPC protocol version. Always `2.0`.
                id:
                  type: integer
                  default: 1
                  description: Request identifier echoed back in the response.
                method:
                  type: string
                  enum:
                    - metal_getFinalityCertificate
                  default: metal_getFinalityCertificate
                  description: JSON-RPC method name.
                params:
                  type: array
                  prefixItems:
                    - type: string
                      default: >-
                        0x4f06f3c2aebd79d3e85b577ad25d0643f469cf8d7a65c5fb29f96de0c4594870
                      description: Finalized block hash.
                  items: false
                  minItems: 1
                  maxItems: 1
                  default:
                    - >-
                      0x4f06f3c2aebd79d3e85b577ad25d0643f469cf8d7a65c5fb29f96de0c4594870
                  description: '`[blockHash]`.'
                  x-default:
                    - >-
                      0x4f06f3c2aebd79d3e85b577ad25d0643f469cf8d7a65c5fb29f96de0c4594870
            example:
              jsonrpc: '2.0'
              id: 1
              method: metal_getFinalityCertificate
              params:
                - >-
                  0x4f06f3c2aebd79d3e85b577ad25d0643f469cf8d7a65c5fb29f96de0c4594870
      responses:
        '200':
          description: >-
            JSON-RPC 2.0 response. Errors are reported in-band via an `error`
            object with `code` and `message` in place of `result`.
          content:
            application/json:
              schema:
                type: object
                properties:
                  jsonrpc:
                    type: string
                    enum:
                      - '2.0'
                  id:
                    type: integer
                  result:
                    type:
                      - object
                      - 'null'
                    description: >-
                      Finality certificate and parsed verification fields, or
                      `null`.
                    properties:
                      blockHash:
                        type: string
                        description: Hash of the finalized block.
                      blockNumber:
                        type: integer
                        description: Finalized block height.
                      headerRlp:
                        type: string
                        description: >-
                          Full RLP-encoded block header. Its Keccak-256 hash
                          equals `blockHash`.
                      certificate:
                        type: string
                        description: Canonical encoded Simplex finalization certificate.
                      epoch:
                        type: integer
                        description: Consensus epoch.
                      view:
                        type: integer
                        description: Finalizing view.
                      parentView:
                        type: integer
                        description: Parent proposal view.
                      participants:
                        type: integer
                        description: Validator-set size indexed by the signer bitmap.
                      signerCount:
                        type: integer
                        description: Number of validators that signed.
                      signersBitmap:
                        type: string
                        description: >-
                          Canonical signer bitmap, least-significant bit first
                          within each byte.
                      signatureEipUncompressed:
                        type: string
                        description: Aggregate G2 signature in 256-byte EIP-2537 encoding.
                      namespace:
                        type: string
                        description: Hex-encoded base consensus signing namespace.
              example:
                jsonrpc: '2.0'
                id: 1
                result:
                  blockHash: >-
                    0x4f06f3c2aebd79d3e85b577ad25d0643f469cf8d7a65c5fb29f96de0c4594870
                  blockNumber: 4242
                  headerRlp: 0xf902...
                  certificate: 0x002a29...
                  epoch: 0
                  view: 42
                  parentView: 41
                  participants: 3
                  signerCount: 3
                  signersBitmap: '0x07'
                  signatureEipUncompressed: 0x0000...
                  namespace: 0x6d6574616c2d636f6e73656e73757301...

````

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