> ## Documentation Index > Fetch the complete documentation index at: https://docs.neynar.com/llms.txt > Use this file to discover all available pages before exploring further. # By FID or cast > Lookup a reaction by its FID or cast. ## OpenAPI ````yaml get /v1/reactionById openapi: 3.0.4 info: title: Farcaster Hub API version: 2.35.0 description: > Perform basic queries of Farcaster state via the REST API of a Farcaster hub. See the [Neynar docs](https://docs.neynar.com/reference) for more details. contact: name: Neynar url: https://neynar.com/ email: team@neynar.com servers: - url: https://snapchain-api.neynar.com security: - ApiKeyAuth: [] tags: - name: Info description: Operations related to hub information. - name: Casts description: Operations related to casts. - name: Reactions description: Operations related to reactions. - name: Links description: Operations related to links. - name: UserData description: Operations related to user data. - name: Fids description: Operations related to FIDs. - name: Storage description: Operations related to storage limits. - name: Usernames description: Operations related to usernames. - name: Verifications description: Operations related to verifications. - name: OnChainEvents description: Operations related to on-chain events. - name: Message description: Operations related to messages. - name: HubEvents description: Operations related to hub events. paths: /v1/reactionById: get: tags: - Reactions summary: By FID or cast description: Lookup a reaction by its FID or cast. operationId: lookup-reaction-by-id parameters: - name: fid in: query description: The FID of the reaction's creator schema: type: integer required: true example: 616 - name: target_fid in: query description: The FID of the cast's creator schema: type: integer required: true example: 616 - name: target_hash in: query description: The cast's hash schema: type: string required: true example: '0xfec8fd3546e1f46cf5ad10a4ff9f5d53a3bbe9be' - name: reaction_type in: query schema: $ref: '#/components/schemas/ReactionType' required: true responses: '200': description: The requested Reaction. content: application/json: schema: $ref: '#/components/schemas/Reaction' default: $ref: '#/components/responses/ErrorResponse' externalDocs: description: Lookup a reaction by its FID or cast url: https://docs.neynar.com/reference/lookup-reaction-by-id components: schemas: ReactionType: type: string description: >- Type of interaction a user can have with content on the Farcaster network. - Like: Express appreciation for the target content. Similar to "likes" or "favorites" on other platforms. - Recast: Share the target content with the user's followers, similar to a "retweet" or "reblog". Helps increase content visibility. default: Like enum: - Like - Recast example: Like Reaction: allOf: - $ref: '#/components/schemas/MessageCommon' - type: object properties: data: allOf: - $ref: '#/components/schemas/MessageDataReaction' - type: object properties: type: $ref: '#/components/schemas/MessageType' required: - type required: - data MessageCommon: type: object properties: hash: title: Hash digest of data pattern: ^0x[0-9a-fA-F]{40}$ type: string example: '0xd2b1ddc6c88e865a33cb1a565e0058d757042974' hashScheme: $ref: '#/components/schemas/HashScheme' signature: title: Signature of the hash digest pattern: ^(?:[A-Za-z0-9+/]{4})*(?:[A-Za-z0-9+/]{2}==|[A-Za-z0-9+/]{3}=)?$ type: string format: byte signatureScheme: $ref: '#/components/schemas/SignatureScheme' signer: title: Public key or address of the key pair that produced the signature pattern: ^0x[0-9a-fA-F]+$ type: string required: - hash - hashScheme - signature - signatureScheme - signer MessageDataReaction: description: >- Represents a user's reaction to content on the Farcaster network. Reactions can be likes or recasts of casts, allowing users to express appreciation or share content with their followers. allOf: - $ref: '#/components/schemas/MessageDataCommon' - type: object required: - reactionBody properties: reactionBody: description: >- Contains the type of reaction (like/recast) and the target content being reacted to. The target can be specified either by castId or URL. allOf: - $ref: '#/components/schemas/ReactionBody' MessageType: type: string description: >- Type of the MessageBody. - MESSAGE_TYPE_CAST_ADD: Add a new Cast - MESSAGE_TYPE_CAST_REMOVE: Remove an existing Cast - MESSAGE_TYPE_REACTION_ADD: Add a Reaction to a Cast - MESSAGE_TYPE_REACTION_REMOVE: Remove a Reaction from a Cast - MESSAGE_TYPE_LINK_ADD: Add a new Link - MESSAGE_TYPE_LINK_REMOVE: Remove an existing Link - MESSAGE_TYPE_VERIFICATION_ADD_ETH_ADDRESS: Add a Verification of an Ethereum Address - MESSAGE_TYPE_VERIFICATION_REMOVE: Remove a Verification - MESSAGE_TYPE_USER_DATA_ADD: Add metadata about a user - MESSAGE_TYPE_USERNAME_PROOF: Add or replace a username proof - MESSAGE_TYPE_FRAME_ACTION: A Farcaster Frame action default: MESSAGE_TYPE_CAST_ADD enum: - MESSAGE_TYPE_CAST_ADD - MESSAGE_TYPE_CAST_REMOVE - MESSAGE_TYPE_REACTION_ADD - MESSAGE_TYPE_REACTION_REMOVE - MESSAGE_TYPE_LINK_ADD - MESSAGE_TYPE_LINK_REMOVE - MESSAGE_TYPE_VERIFICATION_ADD_ETH_ADDRESS - MESSAGE_TYPE_VERIFICATION_REMOVE - MESSAGE_TYPE_USER_DATA_ADD - MESSAGE_TYPE_USERNAME_PROOF - MESSAGE_TYPE_FRAME_ACTION ErrorResponse: required: - code - details - errCode - metadata - name - presentable type: object properties: errCode: type: string presentable: type: boolean name: type: string code: type: integer details: type: string metadata: required: - errcode type: object properties: errcode: type: array items: type: string HashScheme: type: string description: > Type of hashing scheme used to produce a digest of MessageData. - HASH_SCHEME_BLAKE3: Default scheme for hashing MessageData default: HASH_SCHEME_BLAKE3 enum: - HASH_SCHEME_BLAKE3 SignatureScheme: type: string description: |- 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 default: SIGNATURE_SCHEME_ED25519 enum: - SIGNATURE_SCHEME_ED25519 - SIGNATURE_SCHEME_EIP712 MessageDataCommon: description: >- Common properties shared by all Farcaster message types. These properties provide essential metadata about the message's origin, timing, and network context. required: - fid - network - timestamp type: object properties: type: $ref: '#/components/schemas/MessageType' fid: title: Farcaster ID of the user producing the message description: >- The unique identifier (FID) of the user who created this message. FIDs are assigned sequentially when users register on the network and cannot be changed. type: integer format: uint64 example: 2 timestamp: description: >- Seconds since Farcaster Epoch (2021-01-01T00:00:00Z). Used to order messages chronologically and determine the most recent state. Must be within 10 minutes of the current time when the message is created. type: integer format: int64 example: 48994466 network: $ref: '#/components/schemas/FarcasterNetwork' ReactionBody: description: >- Specifies the details of a reaction to content on Farcaster. A reaction must specify its type (like/recast) and either a target cast ID or URL to react to. Only one target (either castId or URL) should be specified per reaction. type: object properties: type: $ref: '#/components/schemas/ReactionType' targetCastId: description: >- The unique identifier of the cast being reacted to. Must be a valid CastId containing the creator's FID and the cast's hash. allOf: - $ref: '#/components/schemas/CastId' targetUrl: title: URL to react to description: >- The URL being reacted to. Used when reacting to external content or when the cast ID is not available. type: string example: https://www.example.com/article required: - type FarcasterNetwork: type: string description: |- Farcaster network the message is intended for. - FARCASTER_NETWORK_MAINNET: Public primary network - FARCASTER_NETWORK_TESTNET: Public test network - FARCASTER_NETWORK_DEVNET: Private test network default: FARCASTER_NETWORK_MAINNET enum: - FARCASTER_NETWORK_MAINNET - FARCASTER_NETWORK_TESTNET - FARCASTER_NETWORK_DEVNET CastId: description: >- A unique identifier for a cast (post) in the Farcaster network, consisting of the creator's FID and a hash of the cast's content. This combination ensures global uniqueness across all casts. required: - fid - hash type: object properties: fid: title: Fid of the user who created the cast description: >- The Farcaster ID (FID) of the user who created the cast. Required to uniquely identify the cast's author in the network. type: integer format: uint64 example: 2 hash: $ref: '#/components/schemas/CastHash' CastHash: description: >- A unique hash that identifies a specific cast within the creator's posts. Generated using HASH_SCHEME_BLAKE3 of the cast's content. pattern: ^0x[0-9a-fA-F]{40}$ type: string example: '0x03aff391a6eb1772b20b4ead9a89f732be75fe27' responses: ErrorResponse: description: An unexpected error response. content: application/json: schema: $ref: '#/components/schemas/ErrorResponse' securitySchemes: ApiKeyAuth: type: apiKey in: header name: x-api-key description: API key to authorize requests x-default: NEYNAR_API_DOCS ````