Tokenizer for GPT-3 is the same as GPT-2:

https://huggingface.co/docs/transformers/model_doc/gpt2#gpt2tokenizerfast

linked via:

https://beta.openai.com/tokenizer

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**UPDATE** March 2023

For newer models, including GPT-3.5 (turbo), GPT-4, and latest embeddings, use `tiktoken` tokenizer with the `cl100k_base` encoding:

https://github.com/openai/tiktoken

A full model-to-encoding mapping can be found [here](https://github.com/openai/tiktoken/blob/main/tiktoken/model.py)