Claude 2.1
Anthropic's 2023 model that pushed context length to 200K tokens
Claude 2.1 is a refresh of Claude 2 that Anthropic released in November 2023, most notable for doubling the context window to 200,000 tokens, roughly 150,000 words or about 500 pages of text in one request, which was among the largest context windows offered by any commercial model at that point. Alongside the longer context, Anthropic said it cut the model’s rate of false statements roughly in half compared to Claude 2, and added a system prompt feature and early support for tool use, letting the model call external functions and APIs as part of a response.
Anthropic priced Claude 2.1 at $8 per million input tokens and $24 per million output tokens, the same rate as Claude 2, and made it available through both the API and the claude.ai chat interface. It served as Anthropic’s flagship model for a few months until the Claude 3 family arrived in March 2024, and it is now considered legacy, but the shift to very long context windows it introduced carried forward into every Claude generation since.