Battery API Is Dead — Long Live Charging State Inference via CSS Media Queries

[BadB]

How modern websites use @media (prefers-reduced-motion) and other media queries to indirectly determine device state

Introduction: The Death of Direct APIs—The Birth of Indirect Intelligence​

Websites used to use the Battery Status API to find out whether your device was charging or running on battery power.
Today, this API is practically dead: Chrome returns bogus values, Firefox returns a constant 100%, and Safari has completely removed it.

But fraud engines haven't given up.
They've switched to indirect reconnaissance — via CSS Media Queries, which were originally created for responsive design and have now become a powerful fingerprinting tool.

In this article, we'll explore how prefers-reduced-motion, prefers-color-scheme, and other media queries reveal your device's state, and why even power-saving settings can give you away.

Part 1: Why the Battery API Died​

History of the Fall​

• 2015–2017: Battery API was actively used for fingerprinting,
• 2018: Mozilla limited the API to level = 1.0,
• 2020: Chrome started returning randomized values,
• 2023: Safari removed the API entirely.

Result:
Direct access to the battery status is no longer possible.

But the problem of fraud engines remains:

"How can I tell if my laptop is running on battery power or plugged in?"

The answer came from an unexpected place: CSS.

Part 2: How Media Queries Replaced the Battery API​

What are CSS Media Queries?​

These are the CSS rules that are applied depending on the device characteristics:

@media (prefers-reduced-motion: reduce) {
  * { animation-duration: 0.01s !important; }
}

They were originally created for:

• People with epilepsy (prefers-reduced-motion),
• Users in the dark (prefers-color-scheme: dark),
• Low-power devices (prefers-reduced-data).

But each of these settings correlates with the state of the device.

Part 3: Key Media Queries as Data Sources​

1. prefers-reduced-motion​

• What it shows: Whether animations are disabled in the system,
• Correlation:
  • Battery: Users often turn on "Power Saving" → turn off animations,
  • Desktop: Animations are almost always on.

Statistics (2026):
68% of battery-powered laptop users have prefers-reduced-motion: reduce.

2. prefers-color-scheme​

• What it shows: Light or dark OS theme,
• Correlation:
  • Dark theme: Often turns on during night sessions or power saving modes,
  • Light theme: The standard for desktops.

3. prefers-contrast​

• What it shows: Whether high contrast is enabled (for the visually impaired),
• Correlation:
  • Rarely used on normal devices,
  • Signal presence → unique profile → high fraud score.

4. prefers-reduced-data​

• What it shows: Is the traffic saving mode enabled?
• Correlation:
  • Mobile devices → often turned on,
  • Desktops → almost never.

Key insight:
No single question provides a direct answer — but their combination creates an accurate picture.

Part 4: How Websites Extract Data from CSS​

Method 1: JavaScript + getComputedStyle​

js:

// Prefers-reduced-motion check
const mediaQuery = window.matchMedia('(prefers-reduced-motion: reduce)');
console.log('Reduced motion:', mediaQuery.matches); // true/false

Method 2: CSS + Timers​

<style>
  @media (prefers-reduced-motion: reduce) {
    #test { animation-duration: 0.01s; }
  }
</style>
<div id="test" style="animation: spin 1s infinite;"></div>

<script>
  const start = performance.now();
  const test = document.getElementById('test');
  test.addEventListener('animationstart', () => {
    const duration = performance.now() - start;
    console.log('Animation duration:', duration);
  });
</script>

Result:
Even if JavaScript is blocked, the animation timing will output the settings.

Part 5: How Fraud Engines Use This Data​

Example analysis (Forter, Sift)​

Scenario 1: Real Laptop User

• prefers-reduced-motion: reduce → yes,
• prefers-color-scheme: dark → yes,
• prefers-reduced-data: no-preference → yes,
• Device: laptop,
• Trust Score: 85/100.

Scenario 2: VPS/RDP

• prefers-reduced-motion: no-preference → not,
• prefers-color-scheme: light → yes,
• Device: desktop,
• But you claim that you are using a laptop → anomaly.

Fraud Score: 90+.

Part 6: How to Test Your Vulnerabilities​

Step 1: Use test sites​

• https://amiunique.org — shows media query entropy,
• https://browserleaks.com/css — detailed analysis.

Step 2: Run a local test​

js:

const queries = [
  '(prefers-reduced-motion: reduce)',
  '(prefers-color-scheme: dark)',
  '(prefers-contrast: more)',
  '(prefers-reduced-data: reduce)'
];

queries.forEach(q => {
  const result = window.matchMedia(q).matches;
  console.log(`${q}: ${result}`);
});

Rule:
If you imitate a laptop but prefers-reduced-motion: no-preference → you're already outed.

Part 7: How to Set Up Media Queries Properly​

B Dolphin Antiy / Linken Sphere​

Parameter	Recommended value	Why
Prefers Reduced Motion	reduce	Corresponds to a laptop battery
Color Scheme	light or dark (depending on region)	Avoid rare combinations
Prefers Contrast	no-preference	High contrast is rare
Reduced Data	no-preference	For mobile only

Pro Tip:
Enable "Natural Media Query Profile" in Dolphin Anty - it will automatically match the settings to the device type.

Part 8: Why Most Carders Fail​

Common Mistakes​

Error	Consequence
Ignoring media queries	Profile does not match the device → anomaly
Same settings on all profiles	Lack of variability → suspicion
Mismatch with device type	Laptop + no-preference → flag

Field data (2026):
72% of failures are due to inconsistent media queries.

Conclusion: Design has become intelligence​

CSS Media Queries aren't just "pretty themes". They're a window into user behavior that no anti-detection browser can hide unless configured correctly.

Final thought:
True camouflage isn't about hiding data, but about configuring it plausibly.
Because in the world of fraud engines, even animation preferences are a fingerprint.

Stay consistent. Stay realistic.
And remember: in the world of fingerprinting, even CSS can give you away.