AI Desk · AI Fingerprinting · Compare
Google: Gemini 3.1 Pro Preview Custom Tools · Google: Gemini 3.8 Flash
Identity similarity: highExact tokenizer agreement · 50/50Exact agreement across every measured string is one strong signal of shared tokenizer lineage. The published settings differ, so the second signal the methodology needs for very high is absent here; the table below shows where they part.
Google: Gemini 3.1 Pro Preview Custom Tools recordGoogle: Gemini 3.8 Flash recordOpen in the interactive bench
Tokenizer fingerprint
50 of 50 mutually clean strings agree| Test string | Google: Gemini 3.1 Pro Preview Custom Tools | Google: Gemini 3.8 Flash | Verdict |
|---|---|---|---|
| en-prose | 14 | 14 | match |
| en-long | 16 | 16 | match |
| spaces-20 | 3 | 3 | match |
| spaces-60 | 4 | 4 | match |
| tabs-20 | 3 | 3 | match |
| newlines-20 | 3 | 3 | match |
| mixed-ws | 9 | 9 | match |
| digits-9 | 9 | 9 | match |
| digits-12 | 12 | 12 | match |
| digits-30 | 30 | 30 | match |
| digits-sep | 12 | 12 | match |
| float-long | 22 | 22 | match |
| zh-common | 10 | 10 | match |
| zh-long | 12 | 12 | match |
| zh-rare | 25 | 25 | match |
| ja-kana | 7 | 7 | match |
| ja-kanji | 9 | 9 | match |
| ko | 11 | 11 | match |
| ru | 12 | 12 | match |
| ar | 10 | 10 | match |
| he | 13 | 13 | match |
| hi | 8 | 8 | match |
| th | 10 | 10 | match |
| el | 13 | 13 | match |
| emoji-basic | 5 | 5 | match |
| emoji-skin | 10 | 10 | match |
| emoji-zwj-family | 7 | 7 | match |
| emoji-zwj-x3 | 21 | 21 | match |
| emoji-flags | 8 | 8 | match |
| emoji-prof | 11 | 11 | match |
| math | 26 | 26 | match |
| boxdraw | 17 | 17 | match |
| combining | 10 | 10 | match |
| cjk-ext-b | 16 | 16 | match |
| surrogates | 27 | 27 | match |
| zalgo | 22 | 22 | match |
| rtl-mix | 5 | 5 | match |
| py-code | 28 | 28 | match |
| py-indent | 18 | 18 | match |
| json | 28 | 28 | match |
| html | 14 | 14 | match |
| regex | 44 | 44 | match |
| camel | 6 | 6 | match |
| snake | 11 | 11 | match |
| rare-word-x5 | 25 | 25 | match |
| repeat-tok | 21 | 21 | match |
| base64 | 34 | 34 | match |
| hex | 16 | 16 | match |
| url | 23 | 23 | match |
| uuid | 36 | 36 | match |
Values are the marginal prompt-token cost of each string with the model's fixed overhead subtracted. An x marks a row excluded as corrupt for that model.
API surface
The declared serving contracts differ| Field | Google: Gemini 3.1 Pro Preview Custom Tools | Google: Gemini 3.8 Flash | Verdict |
|---|---|---|---|
| Context length | 1048576 | 1048576 | ✓ match |
| Max output tokens | 65536 | 65536 | ✓ match |
| Supported parameters | include_reasoning, max_tokens, reasoning, reasoning_effort, response_format, seed, structured_outputs, temperature, tool_choice, tools, top_p | include_reasoning, max_tokens, reasoning, reasoning_effort, response_format, seed, stop, structured_outputs, temperature, tool_choice, tools, top_p | × differs |
| Defaults | {"temperature":null,"top_p":null,"frequency_penalty":null} | {} | × differs |
| Reasoning contract | {"mandatory":true,"supported_efforts":["high","medium","low"],"default_effort":"medium"} | {"mandatory":true,"default_enabled":true,"supported_efforts":["high","medium","low"],"default_effort":"medium"} | × differs |
| Modalities | text+image+file+audio+video->text | text+image+file+audio+video->text | ✓ match |
Method: tokenizer fingerprinting, v1, 50 strings. This page is static and dated; the interactive bench compares any two of the 338 measured models.