AI Radar

Claude 2.1

Retired · Language

Claude 2.1 is an update to Anthropic's Claude 2 language model, released in November 2023 through the API and as the model behind claude.ai. It raised the context window to 200K tokens and added system prompts and a beta tool-use feature; the model card appendix says it builds on Claude 2.0 rather than being a new base model. [1] [2]Claude 2.1 Model Card Appendix, section 1 Primary source

Timeline of Claude 2.1 →

Claims and evidence

  • Released Primary source[1]
  • Deprecated Primary source[3]2025-01-21: Claude 2, Claude 2.1, and Claude Sonnet 3 models [4]January 21st, 2025
  • Retired Primary source[3]2025-01-21: Claude 2, Claude 2.1, and Claude Sonnet 3 models [4]July 21, 2025
  • Status Retired Primary source[3]2025-01-21: Claude 2, Claude 2.1, and Claude Sonnet 3 models
  • Successor of Claude 2 Primary source[1]2x Decrease in Hallucination Rates [2]Claude 2.1 Model Card Appendix, section 1
  • Change · Context length Context window doubled from 100K to 200K tokens; on claude.ai the full window was reserved for Claude Pro users.Compared with Claude 2 Primary source[1]200K Context Window [2]Claude 2.1 Model Card Appendix, section 2
  • Change · Tool use Tool use added as a beta API feature, letting developers define functions or APIs for the model to call.Compared with Claude 2 Primary source[1]API Tool Use
  • Change · Other System prompts introduced, so users can give the model custom instructions and set context such as a role.Compared with Claude 2 Primary source[1]Developer Experience
  • Change · Other Anthropic reports fewer false statements than Claude 2.0 and fewer incorrect answers about long documents.Compared with Claude 2 Primary source[1]2x Decrease in Hallucination Rates
  • Feature Tool useOffered as a beta feature at launch. Primary source[1]API Tool Use
  • Context window 200K tokensOn claude.ai the full 200K window was reserved for Claude Pro users at launch. Primary source[1] [2]Claude 2.1 Model Card Appendix, section 2
  • Parameters Not disclosedNot disclosed by Anthropic. No claim madeNo source
  • Access API, consumer app Primary source[1]

Lineage

Predecessors

Successors

Based on

Not derived from another model.

Variants and derived

None recorded.

Siblings

None recorded.

All ancestors

All descendants

Variants

No variants recorded in this record.

Related AI Radar coverage

AI Radar coverage starts in June 2026; no coverage linked yet.

All model releases from Anthropic on AI Radar →