> ## Documentation Index
> Fetch the complete documentation index at: https://docs.apostate.dev/llms.txt
> Use this file to discover all available pages before exploring further.

# Measure with FingerprintJS Pro

> Read FingerprintJS Pro's suspect score and flags for a persona, from the live tier or from scripts/measure-fpjs.py behind a proxy.

FingerprintJS Pro is the detector Apostate is measured against first. Its public [playground](https://demo.fingerprint.com/playground) shows the verdict for the browser that opens it: a suspect score, and the flags that add to it.

## What the playground reports

| Field                               | Meaning                                                                        | Depends on                 |
| ----------------------------------- | ------------------------------------------------------------------------------ | -------------------------- |
| `suspect_score`                     | Sum of the weights of every flag that fired                                    | everything below           |
| `bot`                               | `not_detected`, `good` or `bad`                                                | the browser and its driver |
| `tampering`, `tampering_ml_score`   | Values that look altered; the model score runs from 0 to 1 and flags above 0.8 | the browser                |
| `anti_detect_browser`               | Traits of anti-detect browsers                                                 | the browser                |
| `anomaly_score`                     | Values no real browser produces                                                | the browser                |
| `virtual_machine`                   | Signs of a virtual machine                                                     | the browser and the host   |
| `developer_tools`                   | DevTools open, or a DevTools client attached                                   | the driver                 |
| `incognito`                         | Off-the-record context                                                         | how the page was opened    |
| `rare_device`                       | A combination of values few visitors have                                      | the persona                |
| `vpn`, `proxy`, `timezone_mismatch` | The IP address and its location against the browser's timezone                 | the network                |

A clean browser on a flagged IP address still scores above zero. Read the flags, not only the score.

## From the live tier

The live tier loads the playground in every browser it tests and records these fields:

```bash theme={null}
cd tests
python3 -m pytest live --live -k fingerprintjs --personas=windows,macos --controls=chrome
```

It passes when none of `bot`, `tampering`, `anti_detect_browser`, `virtual_machine`, `developer_tools` and `incognito` is set. Network flags are recorded and do not fail the test. [Latest results](/testing/results) shows the newest run.

## Behind a proxy with measure-fpjs.py

[`scripts/measure-fpjs.py`](https://github.com/heretic-tech/apostate/blob/main/scripts/measure-fpjs.py) measures one headed launch through a proxy. It looks up the exit's country and timezone through the proxy with `curl`, gives the persona that locale and timezone, loads the playground, and prints every flag.

```bash theme={null}
APOSTATE_PROXY=socks5://user:pass@proxy.example:1080 \
  python3 scripts/measure-fpjs.py --platform windows --seed 42
```

| Option           | Default    | Effect                                       |
| ---------------- | ---------- | -------------------------------------------- |
| `--platform`     | `windows`  | Persona, or `host` for the real machine      |
| `--seed`         | `42`       | Seed                                         |
| `--profile FILE` | none       | Launch a profile you wrote instead of a seed |
| `--window W,H`   | `1536,864` | Window size                                  |
| `--out FILE`     | none       | Save the playground's full text              |
| after `--`       | none       | Extra browser switches                       |

It runs headed, so a Linux server needs Xvfb. Use a fresh proxy session for each run: FingerprintJS remembers a visitor, and a returning visitor with a new machine scores differently from a new one. `APOSTATE_BINARY` points it at a local build.

## Compare fairly

* Measure a control on the same exit: `--platform host` for the real machine, or Google Chrome. Their difference from the persona is what Apostate changes; what they share is the network and the host.
* Use the driver your users use. Under plain Playwright, FingerprintJS reports `developer_tools` on every run; under Patchright, which the packages use, it does not.
* Several runs, several seeds. One run is one sample.