What is a Context Window in LLM?

calendar Apr 10, 2025 · 2 min read · AI basics context window LLMs ChatGPT Context Length Context Window LLM AI concepts AI for beginners  ·
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Have you ever noticed how some AI tools remember things you've just said, while others seem to forget quickly? This ability to remember and keep track of the conversation is managed by something called a Context Window. It is the maximum number of tokens (pieces of text) a large language model (LLM) can process at once.

Imagine you're talking to someone who can only remember the last five sentences you said. After those five sentences, they start forgetting what you said earlier. This limitation is similar to how a context window works for an AI.

A context window is essentially the AI's short-term memory. It determines how much recent information the AI can remember and consider when responding.

  • Better Responses: A larger context window allows AI to understand longer conversations, leading to more relevant and coherent replies.
  • More Accurate Information: With a broader memory, the AI can produce answers based on more complete information.

Think of your interaction with AI like chatting with a friend who has limited short-term memory:

Short Context Window (limited memory) :

You: “My name is Bishworaj.”
AI: “Hi Bishworaj!”

(after a few more interactions)

You: “What’s my name?”
AI: “Sorry, I forgot.”

You: “My name is Bishworaj.”
AI: “Hi Bishworaj!”

(after many interactions)

You: “What’s my name?”
AI: “Your name is Bishworaj!”

A bigger context window requires more computing power. Think of it like having more tabs open on your computer. The more you open, the slower your computer might get. Similarly, larger context windows can make AI slower and more costly to run.

Today, AI models like OpenAI's GPT-4 can remember up to 128,000 tokens. Google’s Gemini 1.5 Pro can remember even more up to 2 million tokens. That’s like being able to recall an entire book!

  • Slower Responses: Larger memory can make the AI slower.
  • Increased Cost: More memory means more computing power, which means higher costs.
  • Security Risks: Bigger context windows may also make AI easier to trick into giving unintended responses.

Context windows shape how effectively AI can interact with us, balancing memory, speed, and cost. Understanding it helps you grasp the capabilities and limitations of the AI tools you use daily.