REVERSE-ENGINEERING THE OPENAI'S GPT-5 TOKENIZER: WHAT 200,000 TOKENS REVEAL ABOUT AEO/GEO

Summary from the TLDR AI newsletter

Text has to pass through a tokenizer before GPT-5.x is able to understand any input. A tokenizer is a compression layer that converts raw text into a sequence of integer IDs. Every design decision baked into the tokenizer has downstream consequences for cost, accuracy, multilingual performance, and hallucination rates. This article looks at OpenAI's open-source tokenizer library, tiktoken, and explains how it works.