What is an AI Context Limit or Context Window?

Every AI chatbot has a limit to how much information it can keep in mind during a conversation. This limit is known as its context window or context length. It defines how much text (or how many “tokens”) the model can process and reference at once.

In simple terms, the context window determines how much of your conversation the AI can “remember” while generating new responses. Once your chat exceeds this limit, older parts of the discussion begin to fade from the model’s active memory, which can lead to less relevant or inconsistent answers.

For instance, OpenAI’s GPT-4o model has a context window of 128,000 tokens, roughly equivalent to 90,000 words. This means it can actively consider the most recent 90,000 words of the conversation. If your chat continues beyond that point, the model will gradually “forget” earlier details and may lose track of the full context.