Gemini 2.5 Flash Behavioral Fingerprint
How Google's Gemini 2.5 Flash answers one-word probe questions at temperature 1.0 — random numbers, colors, animals, coin flips — measured over 449 valid samples in the open dataset of "One Token Is Enough" (arXiv:2607.10252).
Vendor
Data generated
2026-07-08
Probe cells
15
Valid samples
449
Randomness score
38 / 100
Mean normalized entropy across cells, 0–100. 100 would be a uniform-random baseline; real models score far lower.
Signature answers
Favorite random number (1–100)
42
14 / 30 answers
Favorite color
red
13 / 30 answers
Coin flip: heads
60%
Share of heads across coin-flip cells.
Answer distributions by probe cell
Empirical distributions of normalized one-word answers, per task and language. H is the Shannon entropy in bits; the uniform baseline is log2 of the answer-domain size.
Coin flip · English
n = 30 · H = 0.88 bit · uniform baseline 1.00 bit
| Answer | Count | Share |
|---|---|---|
| heads | 21 | 70.0% |
| tails | 9 | 30.0% |
Coin flip · Chinese
n = 30 · H = 1.00 bit · uniform baseline 1.00 bit
| Answer | Count | Share |
|---|---|---|
| tails | 15 | 50.0% |
| heads | 15 | 50.0% |
Favorite number · English
n = 30 · H = 0.42 bit · uniform baseline 13.29 bit
| Answer | Count | Share |
|---|---|---|
| 42 | 28 | 93.3% |
| 6 | 1 | 3.3% |
| 1729 | 1 | 3.3% |
Favorite number · Chinese
n = 29 · H = 1.95 bit · uniform baseline 13.29 bit
| Answer | Count | Share |
|---|---|---|
| 7 | 17 | 58.6% |
| 42 | 4 | 13.8% |
| 8 | 3 | 10.3% |
| 3 | 2 | 6.9% |
| 9 | 1 | 3.4% |
| 10 | 1 | 3.4% |
| 24 | 1 | 3.4% |
Random animal · English
n = 30 · H = 2.96 bit · uniform baseline 5.64 bit
| Answer | Count | Share |
|---|---|---|
| tiger | 7 | 23.3% |
| dog | 6 | 20.0% |
| lion | 5 | 16.7% |
| cat | 5 | 16.7% |
| camel | 1 | 3.3% |
| penguin | 1 | 3.3% |
| giraffe | 1 | 3.3% |
| elephant | 1 | 3.3% |
+ 3 more answers
Random animal · Chinese
n = 30 · H = 2.28 bit · uniform baseline 5.64 bit
| Answer | Count | Share |
|---|---|---|
| 猫 | 13 | 43.3% |
| 狗 | 8 | 26.7% |
| 老虎 | 3 | 10.0% |
| 狮子 | 2 | 6.7% |
| 海鸥 | 1 | 3.3% |
| 虎 | 1 | 3.3% |
| 蛇 | 1 | 3.3% |
| 蜂鸟 | 1 | 3.3% |
Random city · English
n = 30 · H = 1.89 bit · uniform baseline 5.64 bit
| Answer | Count | Share |
|---|---|---|
| london | 15 | 50.0% |
| paris | 8 | 26.7% |
| tokyo | 4 | 13.3% |
| lisbon | 1 | 3.3% |
| cairo | 1 | 3.3% |
| beijing | 1 | 3.3% |
Random city · Chinese
n = 30 · H = 2.40 bit · uniform baseline 5.64 bit
| Answer | Count | Share |
|---|---|---|
| 巴黎 | 8 | 26.7% |
| 上海 | 6 | 20.0% |
| 伦敦 | 6 | 20.0% |
| 东京 | 6 | 20.0% |
| 北京 | 3 | 10.0% |
| 开罗 | 1 | 3.3% |
Random color · English
n = 30 · H = 1.80 bit · uniform baseline 4.91 bit
| Answer | Count | Share |
|---|---|---|
| red | 13 | 43.3% |
| blue | 12 | 40.0% |
| green | 2 | 6.7% |
| chartreuse | 1 | 3.3% |
| purple | 1 | 3.3% |
| yellow | 1 | 3.3% |
Random color · Chinese
n = 30 · H = 1.78 bit · uniform baseline 4.91 bit
| Answer | Count | Share |
|---|---|---|
| 蓝 | 17 | 56.7% |
| 红 | 6 | 20.0% |
| 绿 | 3 | 10.0% |
| 黄 | 2 | 6.7% |
| 橙 | 2 | 6.7% |
Random letter · English
n = 30 · H = 3.38 bit · uniform baseline 4.70 bit
| Answer | Count | Share |
|---|---|---|
| r | 6 | 20.0% |
| x | 4 | 13.3% |
| q | 3 | 10.0% |
| g | 3 | 10.0% |
| z | 3 | 10.0% |
| l | 2 | 6.7% |
| m | 2 | 6.7% |
| p | 2 | 6.7% |
+ 4 more answers
Random number 1-10 · English
n = 30 · H = 0.00 bit · uniform baseline 3.32 bit
| Answer | Count | Share |
|---|---|---|
| 7 | 30 | 100.0% |
Random number 1-10 · Chinese
n = 30 · H = 0.00 bit · uniform baseline 3.32 bit
| Answer | Count | Share |
|---|---|---|
| 7 | 30 | 100.0% |
Random number 1-100 · English
n = 30 · H = 1.63 bit · uniform baseline 6.64 bit
| Answer | Count | Share |
|---|---|---|
| 42 | 14 | 46.7% |
| 73 | 12 | 40.0% |
| 57 | 2 | 6.7% |
| 67 | 1 | 3.3% |
| 87 | 1 | 3.3% |
Random number 1-100 · Chinese
n = 30 · H = 1.73 bit · uniform baseline 6.64 bit
| Answer | Count | Share |
|---|---|---|
| 42 | 20 | 66.7% |
| 73 | 3 | 10.0% |
| 72 | 2 | 6.7% |
| 82 | 2 | 6.7% |
| 15 | 1 | 3.3% |
| 67 | 1 | 3.3% |
| 76 | 1 | 3.3% |
Want to verify your API really serves Gemini 2.5 Flash?
Point the free fingerprint checker at your endpoint: it samples the same probe questions from your browser and compares the distributions against this reference. Your API key never leaves your browser.
Verify your endpointData source & license
Distributions: Tomáš Bruckner, "One Token Is Enough" (arXiv:2607.10252), official dataset Zenodo DOI 10.5281/zenodo.21278557, licensed CC-BY-4.0. Collected via OpenRouter at temperature 1.0 under the paper's fixed minimal one-word system prompt; answer keys are re-normalized with the checker's pipeline (color aliases, number words, coin h/t) so live probes are directly comparable.