notes

Create and Use Farcaster Signers

Published 4/24/2025.

#farcaster #development #tutorial

I got nerdsniped on Farcaster today.

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Simply, @keccers.eth is talking about the Sent from coinbasewallet tag. You generally only see these for 3rd party clients — to the point that @artlu having his own stands out on the timeline.

My curiosity was piqued, I started poking around, and soon I had landed somewhere between

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and

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Like I said — nerdsniped. It didn’t take long after that for @stevedylandev.eth to join the conversation with some helpful resources that he’s put together.

He even posted a video on Youtube as a walkthrough for the process: https://www.youtube.com/watch?v=rPr8A9Ntp1E

I’ve summarized the steps here:

How to post with your own “sent from …​” tag — updated

  1. Clone Cast Keys and configure it

    git clone https://github.com/stevedylandev/cast-keys
cd cast-keys
npm install                       # install deps for Cast Keys
cp .env.v.sample .env.local

    Edit .env.local:

    DEVELOPER_FID=<FID that should appear in “sent from …”>
DEVELOPER_MNEMONIC=<that handle’s 12-word phrase>

  2. Start Cast Keys and create a signer

    npm run dev

    Open http://localhost:3000, click Create Signer, scan the QR in Warpcast, pay the Warps, and copy the private key (omit the leading 0x).

  3. Install the Mast CLI

    Script (one-liner)

    curl -fsSL https://stevedylan.dev/mast.sh | bash

    Homebrew

    brew install stevedylandev/mast-cli/mast-cli

  4. Authorise Mast with your signer

    mast auth
# 1 – enter your personal FID
# 2 – paste the private key

  5. Post from the terminal

    mast new
# type the message → Enter
# optional: up to two URLs → Enter
# optional: channel → Enter

  6. Revoke a signer when necessary
    Warpcast → Settings → Advanced → Manage Connected Apps → select the key → Delete (no cost).

Why run Cast Keys locally?
The hosted tool at castkeys.xyz always uses @castkeys’ credentials, so every post shows “sent from castkeys.” Running it yourself puts your name on the marquee and keeps the keys in your own hands.

And it works. I can now cast with a custom signer. Next step — a vanity account.

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