Definition
Grok is the AI assistant and large language model family built by xAI, available on grok.com, in mobile apps and inside the X social network. Its distinguishing feature is live access to public posts on X alongside regular web search, which makes it the assistant most likely to reflect what people are saying about a brand right now.
Ownership has changed twice in a short time. xAI acquired X in 2025, and SpaceX acquired xAI on February 2, 2026, in a deal Reuters reported valued xAI at $250 billion. The AI business rebranded as SpaceXAI in July 2026, and xAI's website and developer docs now use the name SpaceXSI; the API still runs at api.x.ai. SpaceX's IPO filing said about 117 million monthly active users used Grok's AI features as of March 31, 2026, within roughly 550 million monthly active users across X and Grok combined.
The model line moves quickly. Grok 4 launched in July 2025 with native tool use and real-time search. Grok 4.5 followed in July 2026 and Grok 4.6 in August 2026. Grok 4.7, released September 21, 2026, is xAI's current flagship: it has a 500,000-token context window and a knowledge cutoff of May 2026, according to xAI's model documentation. At launch it was available through the API, the Grok Build coding agent and Cursor, with xAI's model card saying it would reach the consumer Grok app and Grok in X later. Grok 5 has been described as in training but had not been released as of mid-October 2026.
How Grok finds information matters for GEO. xAI's docs state plainly that Grok has no knowledge of current events beyond its training data unless search tools are enabled. In the consumer product, Grok searches both the web and X; developers can turn on separate web_search and x_search tools. For harder questions, Grok's DeepSearch mode (introduced with Grok 3 in February 2025) runs a multi-step investigation and writes a cited report. Each path has its own fetcher, and Grok Search, Grok DeepSearch and GrokBot show up as separate user agents in server logs.
Because X posts are a first-class source, Grok answers can pick up complaints, launch reactions and executive posts within hours, sometimes before any article covers them. That makes sentiment monitoring on X part of AI visibility work, not just social media management. A brand whose public X presence is dormant or out of date leaves Grok to describe it from other people's posts. Our data on social media citations by AI model shows how differently Grok and other assistants draw on social platforms.
Practical steps: keep the brand's X profile and pinned post accurate, respond publicly to recurring complaints, make sure key web pages are crawlable by Grok's fetchers, and compare Grok's answers with ChatGPT and Google AI Mode for the same prompts as part of cross-platform AI visibility tracking. Large gaps usually point to a social narrative the web-based assistants are not seeing.
Examples of Grok
- A consumer electronics brand finds Grok mentions a battery recall rumor that started on X two days earlier, while ChatGPT and Google AI Mode, which rely on news coverage, say nothing about it.
- A fintech startup's founder posts a clear thread explaining new pricing; within a day Grok answers about the company quote the new prices, while other assistants still show the old ones.
- A developer tests Grok 4.7 through the xAI API with x_search enabled to summarize community reaction to a framework release, then disables it to see what the model knows from training alone.
- A GEO analyst sees requests from the Grok-DeepSearch user agent in server logs after a competitor comparison goes viral on X, and checks that the comparison page renders without JavaScript.
