A keyword is the simplest opt-in machine you can run. You promote 'Text JOIN to [number]' on everything. A supporter texts it, your system auto-replies with a welcome and the required disclosures, and their consent is captured with a timestamp. No form, no friction, and the record proves itself.
Why it's the cleanest opt-in
The person took an affirmative action, texting your keyword, which is unambiguous consent. The auto-reply delivers the disclosures (what they'll get, msg/data rates, reply STOP) and confirms the opt-in. It's documented from the first message.
How to set it up
Pick a short, memorable keyword, wire it to a keyword autoresponder that sends the welcome-and-disclosure reply, and put 'Text [KEYWORD] to [number]' on every sign, slide, flyer, and page. Then promote it relentlessly.
Frequently asked questions
What is a text-to-join keyword?
A word (like JOIN) people text to your number to opt in. They text it, receive a confirmation with the required disclosures, and become a documented consented contact.
How do I create a keyword opt-in?
Choose a short keyword, connect it to an autoresponder that sends a welcome with disclosures, and promote 'Text [KEYWORD] to [number]' everywhere supporters see you.
Informational, not legal advice.
Keep reading: How to grow a texting list that's actually yours and How do I get people to opt in to campaign texts.