OpenAI: GPT-3.5 Turbo is OpenAI's model, and its measured tokenizer sits in OpenAI's own signature group alongside its sibling models. Measured models from IBM and Microsoft carry the same vocabulary, which reads as reuse of OpenAI's tokenizer line and questions nobody's authorship; they are listed under "Shares this fingerprint" below.
cl100k_base is an open vocabulary table anyone can build on. Sharing it says which dictionary the model reads with, and nothing about who made the model.
| Signal | Result | Reference |
|---|---|---|
| Tokenizer signature | Exact match with 3 other models | tk_ba918336 |
| API surface | Identical contract to 1 other entry | api_e35a478b |
| Context and output | 16,385 context · 4,096 max output | declared |
| Reasoning contract | None declared | declared |
| Serving providers observed | OpenAI | measured 22 August 2026 |
Click a row to open the full comparison.
An x marks a row excluded as corrupt (caching or provider interference detected during measurement). Overhead subtracted: 7 prompt tokens.
GPT-3.5 Turbo is OpenAI's fastest model. It can understand and generate natural language or code, and is optimized for chat and traditional completion tasks. Training data up to Sep 2021.
Supported parameters
frequency_penaltylogit_biaslogprobsmax_tokenspresence_penaltyresponse_formatseedstopstructured_outputstemperaturetool_choicetoolstop_logprobstop_p
defaults: {}
Cite this page as the evidence record for OpenAI: GPT-3.5 Turbo: the URL is stable, measurements are dated, and revisions append to the history above. Method: tokenizer fingerprinting, v1, 50 strings.
