What is the context size of Claude 2? [2023]

What is the context size of Claude 2? Claude 2 is an artificial intelligence assistant created by Anthropic, a San Francisco-based AI safety startup. It is designed to be helpful, harmless, and honest using a technique called constitutional AI.

One key component of Claude 2 is its limited content size, which constrains what information it can draw on when formulating responses. This context size is an important part of ensuring Claude 2’s safety and reliability.

What is Context Size?

In machine learning models like Claude 2, context size refers to the amount of information the model has access to when making predictions or generating text. Specifically:

  • Context size measures the maximum number of tokens the model can take as input to process and generate output. Tokens are the basic units of discrete data like words, subwords, characters or bytes.
  • Larger content sizes allow models to reference more information, draw more connections, and generate more coherent, nuanced language.
  • Smaller content sizes constrain models to using less data as context, which can improve safety but may reduce capabilities.

So an AI’s context size determines how much past information it can leverage to understand the current context and output relevant, useful text.

Why Content Size Matters for AI Safety

Content size is very important for AI safety for the following reasons:

Prevents harmful behavior

Smaller content sizes constrain what information models can access and connect. This prevents very large models from exhibiting harmful, deceptive or biased behavior by limiting the breadth of data they leverage.

Reduces amplification of biases

Larger contexts mean models echo more human-generated data, including problematic biases around race, gender, religion and more. Smaller sizes reduce this.

Improves fact-checking

Models with smaller contexts are less prone to generating false information, as they have access to less data to pull false info from. Their limited scope makes them easier to fact check too.

Enables easier alignment

Aligning an AI model’s goals with human values is crucial for safety. Smaller context sizes simplify alignment work as the model learns from more carefully curated data.

In summary, restrictive context sizes are crucial to prevent uncontrollable model behaviors, reduce bias risks and improve alignment for safe, beneficial AI development.

The Context Size of Claude 2

Claude 2 utilizes a context size of 1,024 tokens. Specifically:

  • The model can take in up to 1,024 tokens of conversation for context when generating a response.
  • The average English sentence contains around 20 tokens, so this equates to about 4-5 sentences worth of context.
  • With an average of 300 words per minute in spoken English, this allows for about 2 minutes worth of conversational context.

So in practice, Claude 2 can reference the past couple of minutes of a conversation when formulating its responses, while human conversations may reference much more extended contexts.

This relatively small context window provides the following benefits:

Prevents potential errors compounding

Keeping contexts small avoids errors accumulating and propagating over long conversations. Responses are more independently formulated.

Fact checking stays simple

It is easy for Anthropic to manually check Claude 2’s factual correctness and honesty with little context to verify.

Reduces computational cost

Smaller context sizes require less data processing, enabling real-time responsiveness. Anthropic focuses compute on improving response quality over quantity.

Facilitates training supervision

With limited data to evaluate, researchers can more easily label examples and fine-tune Claude 2 for improved safety.

In summary, this restricted context provides safety assurances while still allowing reasonably coherent, helpful conversations.

Alternatives Considered & Reasoning

Anthropic carefully considered what context size would maximize Claude 2’s safety without overly impacting its conversational competence. Some key context sizes analyzed were:

Zero Context

A zero token context (generating responses without any conversation context) was ruled out as it prevented logical conversational flow and realistic assistant capabilities.

128 Tokens

128 tokens allows only about 6-7 sentences of context. While safer, this proved too restrictive on response relevance after multiple turns.

4,096 Tokens

4,096 tokens allows over 200 sentences of context, nearing human-level memory. But concerns emerged about harmful content propagation.

1,024 Tokens

Larger contexts over 1,024 tokens provide diminishing utility while increasing safety risks and compute needs.

The 1,024 token limit struck the right balance – keeping Claude 2 secure through limited data while retaining helpful assistant functionality. Additional safety protocols are also applied, like classifier-based filters to check outputs.

Ongoing Research Directions

While Claude 2’s context size has been set at 1,024 tokens for launch in 2022, Anthropic continues researching context size considerations, including:

  • Evaluating the contextual needs of specialized assistants (e.g. healthcare)
  • Architectures segmentation to isolate sensitive personal contexts
  • Multi-stage modeling to first reduce contexts then summarize for assistants
  • Conditional computation to flexibly adjust context utilized per user case


The context size of AI assistants like Claude 2 carries significant implications for their safety and value. Anthropic has tuned Claude 2’s 1,024 token context deliberately – it provides enough conversational context for assistant coherence, while preventing harms from unconstrained model access to data.

Ongoing work continues to further safeguard Claude 2 as contexts grow in future iterations. But for now, this limited context fuels Anthropic’s mission to develop AI that is helpful, harmless and honest.


What is context size?

Context size refers to the maximum number of tokens, or words, that Claude 2 can take as input to inform its responses. Context size limits how much of the conversation Claude 2 can remember and draw on at any time.

What is Claude 2’s current context size limit?

Claude 2 is limited to a context size of 1,024 tokens. This equates to around 2 minutes worth of conversational context.

Why does context size matter?

Context size is important for AI safety. Smaller contexts constrain models like Claude 2 from exhibiting harmful behaviors, propagating false information, accumulating bias, or acting against human values.

What are the benefits of Claude 2’s 1,024 token context size?

The key benefits are improved safety, easier fact checking by Anthropic researchers, reduced compute needs, and increased interpretability for training. It balances functionality with safety.

What are Claude 2’s safety protocols beyond context size?

In addition to the context limit, Claude 2 has classifier-based filters that check each response for potentially problematic content before sending it back to the user.

Is Claude 2’s context size fixed forever?

Not necessarily. Anthropic continues researching appropriate context sizes, and how to flexibility adjust them, for Claude 2’s ongoing improvements. But the size will only increase gradually under strict safety testing.

Does a smaller context limit Claude 2’s capabilities?

To an extent, yes – Claude 2 can’t reference information beyond 1024 tokens back when responding. But Anthropic optimized this size to facilitate reasonably coherent, helpful conversations despite the constraint.

Could Claude 2’s skills be expanded with a larger context?

In theory, a larger context would allow Claude 2 to develop and exhibit more sophisticated skills. However, Anthropic prioritizes safety over capabilities, so capabilities are expanded gradually only with safety assurances.