What is X (Twitter)? Definition, history and how it works

How does X (Twitter) work?

X works as a public, real-time feed of short posts that anyone can reply to, repost or quote. Users follow accounts, and the app mixes their posts with algorithmic recommendations in the For You tab. A standard post has a 280-character limit (raised from 140 in 2017), while X Premium subscribers can post up to 4,000 characters. Posts can include images, video, polls and links, and X Spaces adds live audio rooms.

Hashtags, trending topics and Communities group conversations by subject, which is why X is often the first place where a viral story or a brand crisis appears.

History of X: from Twitter to xAI

X began as Twitter, founded in 2006 by Jack Dorsey, Noah Glass, Biz Stone and Evan Williams. The table shows the key changes.

After the rebrand, X made verification part of a paid subscription, added long posts, creator monetisation and calls, and built in xAI’s Grok chatbot.

X users in numbers

X reaches about 7.1% of the world’s population with its ads, according to DataReportal’s January 2025 data, and that reach fell by 5.3% in 12 months. The audience is 63.7% male. The largest markets are the United States (104 million), Japan (70.9 million) and Indonesia (25.2 million). In Poland, DataReportal’s Digital 2026 report counts 4.59 million users reachable with X ads, which is 14.2% of adults, down 8.2% year on year. DataReportal notes that these are advertising audiences, not monthly active users.

X in marketing, SEO and AI search

X matters to marketers because it reaches journalists, founders, politicians and niche experts who shape opinion. The H3s below cover the three main uses.

X ads

X Ads Manager offers Promoted Ads (image, video, carousel and text), Vertical Video Ads, X Amplify pre-roll sponsorships, Timeline and Spotlight Takeovers, X Live, Dynamic Product Ads and Collection Ads. Targeting by keywords and by followers of specific accounts works well for B2B and tech brands, often next to LinkedIn campaigns.

X and organic visibility

Google shows public X posts in search results for news and trending queries, so an active profile can appear for brand searches. Links in posts are nofollow, so X is a distribution channel, not a source of ranking power.

X and AI search

Grok reads public X posts in real time and cites them in answers, which makes X a direct input for one AI assistant. In my AI SEO work I treat consistent expert posts on X as part of Generative Engine Optimization: if Grok is asked about a product category, it pulls from what people say on X. More on this on the AI SEO services page.

X vs Threads

Brands that want text-based reach often run both, and compare results against Threads.

If you need X to work alongside other channels, see my approach to social media marketing.