# Claude 2.1

Claude 2.1 is an AI model released by Anthropic on Nov 21 2023. It has a 200k context window.

## Facts

| Field | Value |
| --- | --- |
| Model | Claude 2.1 |
| Developer | Anthropic |
| Release date | Tuesday, Nov 21 2023 |
| Licensing | Proprietary |
| Context window | 200k |

## About Claude 2.1

Claude 2.1, released November 21, 2023, doubled the context window to 200,000 tokens — about 150,000 words, or more than 500 pages — the largest of any commercially available model at the time. It landed in the same week that OpenAI was consumed by the firing and reinstatement of Sam Altman, and Anthropic used the opening to push long-document work as the thing Claude was for: contract review, financial filings, entire technical specifications in a single prompt.

Anthropic published no new academic benchmark scores with the release, leading instead on reliability: a 2x reduction in false statements compared with Claude 2.0, and a 30% drop in incorrect answers on document-comprehension tasks. The release also brought system prompts and a beta of tool use. Independent needle-in-a-haystack testing published the day after launch found recall degrading once prompts ran past roughly 90K tokens, and varying with where in the document the buried fact sat — an early public demonstration that having a large context window and using all of it reliably are two different problems. Anthropic followed up two weeks later with prompting guidance that recovered much of the gap.

## Questions and answers

### When was Claude 2.1 released?

Claude 2.1 was released by Anthropic on Tuesday, Nov 21 2023.

### Who made Claude 2.1?

Claude 2.1 was built by Anthropic. AI safety company building the Claude family of models. Founded in 2021 by former OpenAI researchers.

### What is the context window of Claude 2.1?

Claude 2.1 has a context window of 200k — roughly 150,000 words of text. That is the maximum amount of input plus output the model can hold in a single request.

### Is Claude 2.1 open source?

No. Claude 2.1 is a proprietary model. The weights are not published — it is available only through the provider's own API, apps, or partner platforms.

### What came before and after Claude 2.1?

Anthropic's previous tracked release was Claude Instant 1.2 on Aug 9 2023, 104 days earlier. It was followed by Claude 3 Haiku on Mar 4 2024.


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Canonical page: https://aireleasetracker.com/model/anthropic/claude-2.1
Full dataset: https://aireleasetracker.com/llms-full.txt · JSON: https://aireleasetracker.com/models.json
Source: AI Release Tracker (https://aireleasetracker.com). Most benchmark scores come from lab launch material; gathered results identify the leaderboard that published them.