X (Twitter)

X is a website and an app where people publish short public messages. Anyone can read these posts, share them further, or comment on them. The service used to be called Twitter, and the posts were called tweets. In July 2023 it was renamed X, shortly after entrepreneur Elon Musk had bought the company for around 44 billion dollars. Unlike a newspaper, there is no editorial team that checks content beforehand. That’s exactly what makes X fast — and at the same time susceptible to rumors.

Why stock markets and newsrooms watch X

X is small compared to Instagram or TikTok. Depending on how you count, it has a few hundred million active users, while TikTok has over a billion. Nevertheless, it is influential because an especially large number of journalists, politicians, executives, and researchers post there. A piece of news doesn’t need to take a detour through a press office there.

For financial markets, this has direct consequences. Elon Musk has repeatedly moved stock and crypto prices with individual posts. In 2018 he wrote that he wanted to take Tesla private — the US Securities and Exchange Commission imposed a multi-million-dollar fine over this, because the statement misled investors. Cases like this show: a sentence on X can legally be treated like an official corporate announcement.

For the AI industry, X is important for a second reason. Users' posts serve as training material, i.e., sample texts from which language models learn. Musk founded his own AI company, xAI, whose chatbot Grok is built directly into X. Anyone who writes on X thereby indirectly supplies raw material for its training.

Timeline, algorithm, and the blue checkmark

You follow other accounts and see their posts in a list, the timeline. However, this list is not purely chronological. A recommendation system sorts it: a program estimates for each post how likely you are to click on it, and shows the most promising ones first. This sorting is colloquially called the algorithm.

Reach arises mainly through resharing. When you share a post, your followers see it, and their followers can share it again. This way, a post from an unknown account can reach millions of people within hours. The growth is avalanche-like, not steady.

A common misconception concerns the blue checkmark next to the profile name. On Twitter, it used to confirm that an account really belonged to the named person. Since 2023 it can be purchased via subscription. It is thus no longer proof of authenticity, but a paid feature — posts from such accounts are additionally shown preferentially.

X in news, prices, and regulation

In everyday life, you usually encounter X indirectly. If an article states that someone “commented on X,” it means such a short post. Screenshots of X posts also constantly end up on WhatsApp or Instagram. In the process, the source is often lost, and fake screenshots are easy to produce.

In the business press, X comes up as an example of platform regulation. The EU has enacted rules with the Digital Services Act that require large platforms to act against illegal content and to disclose their recommendation systems. The EU Commission has proceedings underway against X regarding this. Violations can result in fines calculated as a percentage of global revenue.

It’s important to distinguish X from similar services. Bluesky and Mastodon function almost the same on the surface, but are technically organized differently: on Mastodon, many independent servers jointly operate the network. Threads by Meta is a direct competitor with the same short-message principle. Comparing these services is a recurring topic in tech news.