Context window

The context window is how much text an AI model can consider at once, including your prompt, any documents and the conversation so far.

In practice: It is measured in tokens. A small window means the model forgets the start of a long chat or cannot read a long report in one go; a large window lets it work with whole contracts, codebases or books. When a conversation exceeds the window, older parts are dropped or summarised.

Why it matters when picking a tool

If you work with long documents, a large context window matters more than almost any other feature. Tools that summarise PDFs, review contracts or answer questions about a codebase depend on it. Check the limit on the plan you are paying for, which can be lower than the model's maximum.