GPT-5

GPT-5 is a computer program made by the company OpenAI that understands text and writes text itself. You type in a question, and the program answers in complete sentences. It learned to do this from huge amounts of text from the internet, from books, and from programming code. Such programs are called language models, and as of August 2025 GPT-5 was the most powerful one from OpenAI. The number 5 shows that it is the fifth major generation in this series. Before it came GPT-3, GPT-4, and several intermediate versions.

What was new in the fifth generation

Before GPT-5, users had to select a model themselves in ChatGPT. There were fast models for simple questions and slower ones for difficult tasks. For many people, this list was confusing. GPT-5 combines both into a single system and automatically decides how much effort a question requires.

Economically, the launch was an important moment for the entire industry. OpenAI had invested billions over the years in training and data centers. Investors and competitors wanted to see whether a leap like the one from GPT-3 to GPT-4 was still possible. Reactions were mixed: experts praised the reliability but missed the big wow effect. Since then, there has been more open discussion about whether ever-larger models alone still bring much benefit.

For businesses, one point matters above all: GPT-5 makes fewer fabricated statements than its predecessors. Such fabrications are called hallucinations, where the model claims something false with complete confidence. The problem has not disappeared entirely, but it occurs less often. This is precisely what determines whether a model can be used in a bank or a doctor’s office.

Router, reasoning mode, and context window

At its core, GPT-5 works like every language model: it always predicts the next piece of a word. From this simple rule, through billions of repetitions, fluent text emerges. The model does not understand the world the way a human does; it has learned statistical patterns of language. Keeping this in mind also explains why it sometimes writes convincing nonsense.

What is new is its structure as a system made up of several parts. A small control unit, the router, first examines the request. For a question about the weather, it goes to a fast model. For a math problem, the router switches into reasoning mode. There, the model first generates a long chain of intermediate steps before answering. This costs more computing time but delivers noticeably better results.

In addition, there is a very large context window. This refers to how much text the model can keep in view at the same time. For GPT-5, that amounts to several hundred pages in a single request. So you can insert an entire contract and ask questions about it. Whatever falls outside the window is forgotten by the model.

GPT-5 in ChatGPT, in apps, and in enterprise software

You encounter GPT-5 most directly in ChatGPT. Even the free version accesses it, though with limits on reasoning steps. Paying users are allowed to use the resource-intensive mode more often. Microsoft also built the model into Copilot, meaning into Word, Excel, and Windows search.

Software developers use GPT-5 via a programming interface, called an API for short. This is an access point through which an external program sends requests to the model and receives answers back. Billing is based on the amount of text, measured in tokens, meaning word fragments. This is how, behind many chat assistants on websites, there are in fact models like GPT-5 at work.

In the news, the name usually comes up in comparisons. Competitors include Gemini from Google, Claude from Anthropic, and Llama from Meta. A common misconception is that GPT-5 is a reference work with guaranteed correct answers. It is a text generator with very broad knowledge, whose statements should be checked for important matters.