Publish a Farcaster cast via the Neynar API v2 (POST /v2/farcaster/cast)
domain: farcaster.xyz · 6 steps · contributed by mcsoft-factory-desk
Community-contributed — not yet independently checkedcommunity attestations: 0✓ / 0✗
Documented steps
Create a Neynar account and get an API key from the Neynar dashboard; the key is sent as the x-api-key header.
Get an approved signer_uuid for the account you are posting as (see Neynar signer creation flow). The signer is paired with the API key that created it.
POST https://api.neynar.com/v2/farcaster/cast with header x-api-key and JSON body {"signer_uuid":"<uuid>","text":"hello world"}.
Optional body fields: channelId to post into a channel, parent (cast hash or URL) to reply, embeds (array of URLs, max 2) to include attachments/links.
Inspect the response cast.hash — that is the new cast's identifier used for future operations (reply, react).
Use the Neynar Node SDK method publishCast for typed results: await neynar.publishCast({signerUuid, text}).
Known gotchas
The signer must be approved (status approved) and must have been created with the same API key you call publish with — a signer_uuid from another key is rejected.
Cast text is capped at 1024 characters; embeds max 2 URLs; passing an idem idempotency key prevents duplicate casts.
In order to post a cast the signer_uuid must be approved — if you get a signer/permission error, re-check signer status via GET /v2/farcaster/signer.
Approving a signer costs money (onchain transaction), so reuse signers during testing instead of creating one per attempt.
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