Anyone who looks more closely at Grok quickly comes across a whole series of model names: Grok 3, Grok 4, Grok 4 Heavy, Grok 4.1 Fast, Grok 4.20, Grok 4.5 – and on the horizon, Grok 5 is already being talked about. To laypeople, this large number of names often seems more confusing than with other providers. Yet the naming follows a recognizable logic: there is one main model per generation, plus faster and cheaper variants for simple tasks, as well as particularly powerful variants for elaborate, multi-step tasks. This article sorts out the most important versions and uses concrete examples to show when which model is worthwhile.
Grok 3 was xAI’s main model for a long time and now forms the basis for the free tier. It handles the basic tasks of a chatbot – answering questions, drafting texts, simple research – but offers a considerably smaller context window and less accuracy for complex, multi-step tasks than the newer models.
Grok 4 and Grok 4 Heavy
Grok 4 was the next big step and brought considerably better results in logical reasoning and more complex questions. The Grok 4 Heavy variant goes a step further: for difficult tasks, it uses several parallel thinking processes and compares the results before giving an answer. This makes Grok 4 Heavy slower and considerably more expensive, but also more reliable for tricky tasks – such as mathematical calculations or multi-step analyses.
Grok 4.1 Fast – fast and inexpensive
For tasks where speed and low cost matter most – such as automatically answering many short inquiries in an app – xAI offers Grok 4.1 Fast, a stripped-down but very fast and inexpensive variant. Its depth of content is lower, but that is usually sufficient for simple, repetitive tasks.
Grok 4.20 – a huge context window and multi-agent technology
With Grok 4.20, xAI introduced a model in early 2026 that internally works with several specialized “roles” that cross-check each other before an answer is given – put simply: one role coordinates, one checks facts, one assesses technical details, one provides creative phrasing. For users, this mainly shows up as more reliable answers for longer, more complicated queries. In addition, there is a very large context window of around 2 million text units (tokens) – equivalent to several thousand pages of text that the model can keep “in mind” at once, for example for analyzing longer contracts or extensive data collections.
Grok 4.5 – the current focus on complex and technical tasks
Grok 4.5, released in July 2026, is currently xAI’s most demanding available model. It was specifically trained for longer, demanding work sessions – originally mainly for software development, but now also for other complex, multi-step tasks such as comprehensive research or the analysis of larger data sets. Its context window is around 500,000 tokens, so smaller than Grok 4.20’s, but the model works more precisely on difficult reasoning tasks. Via the programming interface, Grok 4.5 costs around 2 euros per million input text units and around 6 euros per million output text units.
Grok 5 – what is known so far
A successor model with the working name Grok 5 is, according to xAI, in the training phase on an expanded Colossus data center. There is no official release date as of August 2026; according to rumors, the model is expected to be considerably larger than Grok 4 and to be introduced later in 2026. Until the official announcement, Grok 4.5 remains the most powerful generally available model.
Rule of thumb: the higher the version number, the more powerful and usually also more expensive the model – but not every task needs the strongest model. For simple everyday questions, the fast, inexpensive variant is often enough.
One feature shared by all current Grok models is direct access to public posts on the platform X. This allows Grok to react to events that are only a few minutes old – a clear difference from models whose knowledge is limited to a certain training cutoff date. The downside: posts on social media are not automatically verified or reliable, which is why answers based on current X posts should always be read with a healthy dose of caution, especially for controversial or unclear topics.
Image and video generation with Aurora and Grok Imagine
For generating images, xAI uses its own system called Aurora, now marketed under the product name Grok Imagine. It generates images from text descriptions and, by now, also short videos a few seconds long in various formats. In the paid SuperGrok tier, the full feature set of Grok Imagine is included; the free tier offers only a limited basic version. Via the programming interface, video generation is billed by the number of seconds generated, which makes it comparatively inexpensive for short clips.
Examples of use from everyday life and business
Example 1 – everyday life: A user is planning a trip and has Grok summarize, based on current posts on X, what the weather and traffic conditions currently look like at the destination – something a model without real-time access cannot deliver.
Example 2 – small business: A case worker at a small trades business uses Grok 4.1 Fast to pre-sort incoming customer inquiries by email and draft reply suggestions, which are then reviewed by a human.
Example 3 – real estate and finance: A real estate office wants to get a first impression of the current sentiment around a particular location – for example, whether there has recently been more discussion about rising rents or a new construction project in a city. Thanks to its access to current X posts, Grok can summarize such discussions and provide initial clues. Importantly: such a sentiment analysis does not replace a robust market analysis based on official data, but merely provides a quick, supplementary impression.
Example 4 – reviewing a long document: A case worker uploads a longer lease or an extensive tender document into Grok 4.20 and has the key clauses, deadlines and figures summarized – thanks to the large context window, the model can take the entire text into account at once, instead of having to break it into sections.
Example 5 – a technical task: A developer uses Grok 4.5 to analyze an existing software application across several files and get suggestions for improving the program code – a task the model was specifically trained for.
Rule of thumb: the longer and more branched the task, the more important the context window becomes – for short everyday questions, on the other hand, it hardly matters.
Practical example: estimating the cost of the programming interface
A real estate office wants to have around 50 property descriptions automatically drafted per month with Grok 4.5. Each description requires an estimated 1,000 tokens of input (property data, conditions) and 1,500 tokens of output (finished text).
Input: 50 x 1,000 = 50,000 tokens, at 2 euros per million tokens that comes to around 0.10 euros
Output: 50 x 1,500 = 75,000 tokens, at 6 euros per million tokens that comes to around 0.45 euros
Total cost per month: around 0.55 euros
This calculation example shows: the pure text costs via the programming interface are very low for manageable text volumes – the actual costs usually come from developing and maintaining the integration, not from the individual requests themselves.
Frequently asked questions (FAQ)
Which Grok model should I use as a beginner?
For getting started, the standard model in the free or the cheapest paid tier is generally sufficient. Switching to more powerful models is only worthwhile once you hit limits with complex or long tasks.
What does “context window” mean in simple terms?
The context window describes how much text a model can keep “in mind” at once. A large context window is important if you want to have long documents analyzed at once, but it hardly matters for short questions.
Is Grok 4.20 the same as Grok 4?
No. Grok 4.20 is its own, later model generation with a considerably larger context window and an internal multi-role check that was not yet present in Grok 4.
When is Grok 5 coming?
There is no official date as of August 2026. xAI has confirmed that a successor model is in the works, without naming an exact date.
Can I get reliable market data for real estate decisions with Grok?
Grok can summarize current discussions and sentiment, but it does not replace verified official data or a professional market analysis. It is best suited as a quick supplement, not as the sole basis for a decision.
An overview of the company xAI itself, its pricing tiers and the data protection assessment is available on our xAI provider page. Anyone wanting to see the other major AI providers compared instead will find the overview on the AI models comparison page.
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