OpenAI: GPT-4.1 Nano is OpenAI's model. Its measured tokenizer sits with the GPT group, which is evidence that it builds on the GPT tokenizer. Tokenizer reuse is normal engineering, open vocabularies travel between labs, and this says nothing against OpenAI's authorship of the model itself.
| Signal | Result | Reference |
|---|---|---|
| Tokenizer signature | Exact match with 9 other models | tk_d1411c9d |
| API surface | Identical contract to 2 other entries | api_9c6f5f7f |
| Context and output | 1,047,576 context · 32,768 max output | declared |
| Reasoning contract | None declared | declared |
| Serving providers observed | OpenAI | measured 21 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.
For tasks that demand low latency, GPT‑4.1 nano is the fastest and cheapest model in the GPT-4.1 series. It delivers exceptional performance at a small size with its 1 million...
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Cite this page as the evidence record for OpenAI: GPT-4.1 Nano: the URL is stable, measurements are dated, and revisions append to the history above. Method: tokenizer fingerprinting, v1, 50 strings. The raw data behind every figure is on the data page.
