POST
/
v1
/
submitMessage
curl --request POST \
  --url https://hub-api.neynar.com/v1/submitMessage \
  --header 'Content-Type: application/octet-stream' \
  --header 'x-api-key: <api-key>'
{
  "data": {
    "fid": 2,
    "timestamp": 48994466,
    "network": "FARCASTER_NETWORK_MAINNET",
    "castAddBody": {
      "embedsDeprecated": [
        "<string>"
      ],
      "mentions": [
        2
      ],
      "parentCastId": {
        "fid": 2,
        "hash": "0x03aff391a6eb1772b20b4ead9a89f732be75fe27"
      },
      "parentUrl": "chain://eip155:1/erc721:0x39d89b649ffa044383333d297e325d42d31329b2",
      "text": "<string>",
      "mentionsPositions": [
        123
      ],
      "embeds": [
        {
          "castId": {
            "fid": 2,
            "hash": "0x03aff391a6eb1772b20b4ead9a89f732be75fe27"
          }
        }
      ]
    }
  },
  "hash": "0xd2b1ddc6c88e865a33cb1a565e0058d757042974",
  "hashScheme": "HASH_SCHEME_BLAKE3",
  "signature": "aSDinaTvuI8gbWludGxpZnk=",
  "signatureScheme": "SIGNATURE_SCHEME_ED25519",
  "signer": "<string>"
}

Authorizations

​
x-api-key
string
header
default:NEYNAR_API_DOCS
required

API key to authorize requests

Body

application/octet-stream · file
A Message is a delta operation on the Farcaster network. The message protobuf is an envelope that wraps a MessageData object and contains a hash and signature which can verify its authenticity.

The body is of type file.

Response

200
application/json
A successful response.

A Message is a delta operation on the Farcaster network that represents a state change. Messages are the fundamental unit of data in Farcaster and can represent various actions like:

  • Creating or removing casts (posts)
  • Adding or removing reactions
  • Following or unfollowing users
  • Updating profile data
  • Verifying Ethereum addresses

Each message contains:

  • A MessageData object with the actual content
  • A hash of the content for integrity verification
  • A cryptographic signature to prove authenticity
  • The signer's public key for verification

Messages are immutable once created and form an append-only log of all user actions on the network.

​
data
object
required

Represents a new cast (post) being created in the Farcaster network. A cast can include text content, mentions of other users, embedded URLs, and references to parent posts for replies.

​
hash
string
required
Example:

"0xd2b1ddc6c88e865a33cb1a565e0058d757042974"

​
hashScheme
enum<string>
default:HASH_SCHEME_BLAKE3
required

Type of hashing scheme used to produce a digest of MessageData. - HASH_SCHEME_BLAKE3: Default scheme for hashing MessageData

Available options:
HASH_SCHEME_BLAKE3
​
signature
string
required
​
signatureScheme
enum<string>
default:SIGNATURE_SCHEME_ED25519
required

Type of signature scheme used to sign the Message hash

  • SIGNATURE_SCHEME_ED25519: Ed25519 signature (default)
  • SIGNATURE_SCHEME_EIP712: ECDSA signature using EIP-712 scheme
Available options:
SIGNATURE_SCHEME_ED25519,
SIGNATURE_SCHEME_EIP712
​
signer
string
required