Anthropic Tokenizer TypeScript — AI skill for Claude Code

Anthropic TypeScript Tokenizer

[](https://npmjs.org/package/@anthropic-ai/tokenizer)

⚠️ This package can be used to count tokens for Anthropic's older models. As of the Claude 3 models, this algorithm is no longer accurate, but can be used as a very rough approximation. We suggest that you rely on `usage` in the response body wherever possible.

Installation

npm install --save @anthropic-ai/tokenizer
# or
yarn add @anthropic-ai/tokenizer

Usage

import { countTokens } from '@anthropic-ai/tokenizer';

function main() {
  const text = 'hello world!';
  const tokens = countTokens(text);
  console.log(`'${text}' is ${tokens} tokens`);
}
main();

Status

This package is in beta. Its internals and interfaces are not stable and subject to change without a major semver bump; please reach out if you rely on any undocumented behavior.

We are keen for your feedback; please email us at [support@anthropic.com](mailto:support@anthropic.com) or open an issue with questions, bugs, or suggestions.

Requirements

The following runtimes are supported:

• Node.js version 12 or higher.
• Deno v1.28.0 or higher (experimental). Use import { countTokens } from "npm:@anthropic-ai/tokenizer".

If you are interested in other runtime environments, please open or upvote an issue on GitHub.