Tiktokenizer

Anthropic Claude · Local text estimate

Claude Fable 5 Token Counter

Claude Fable 5 uses Anthropic's newer tokenizer. Estimate supported inputs with Messages count_tokens for your model and request structure, then check actual Messages usage. The local no-key tool offers an English-text planning estimate from Anthropic's documented ratios.

Accuracy note

The local count is an English-text heuristic: characters ÷ 3.5 × 1.3, rounded up, based on Anthropic's newer-tokenizer guidance. It provides no model token IDs or chat overhead and may differ substantially for non-English text or code. For model-aware input counting use Anthropic count_tokens; actual Messages usage can differ.

Official counting docs →

Frequently asked questions

How do I count Claude Fable 5 tokens?

Use Anthropic's Messages token counting endpoint and pass Claude Fable 5 as the model.

Did Claude Fable 5 change tokenizers?

Yes. Anthropic documents that Fable 5 uses the newer tokenizer introduced with Claude Opus 4.7.

Is the token counting endpoint billed?

Anthropic currently documents token counting as free, subject to rate limits; check the official documentation for changes.