https://techcrunch.com/2023/12/07/x-begins-rolling-out-grok-its-rebellious-chatbot-to-subscribers/

Grok, a ChatGPT competitor developed by xAI, Elon Musk’s AI startup, has officially launched on X, the site formerly known as Twitter.

Grok began rolling out late this afternoon to X Premium Plus subscribers in the U.S., “Premium Plus” being X’s plan that costs $16 per month for ad-free access to the social network. Longtime subscribers will get priority access to Grok, X said, with the rollout expected to wrap up in the next week.