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Overview

Device fingerprinting creates a unique identifier for each device accessing your application, allowing you to track the same device across multiple signups and detect multi-accounting.
Fingerprints are automatically collected by client SDKs. Server-side SDKs receive fingerprints from the client.

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What We Track

Device fingerprints are built from browser and hardware signals:
  • Browser user agent, timezone, and language
  • Screen resolution and color depth
  • Canvas and WebGL rendering
  • CPU cores and device memory
  • Touch support and hardware capabilities

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API Response

{
  "checks": {
    "device": {
      "pass": true,
      "latency": 12.5
    }
  },
  "metadata": {
    "fingerprintHash": "abc123def456",
    "previousSignups": 0
  }
}
When device reuse is detected: 
{
  "checks": {
    "device": {
      "pass": false,
      "latency": 15.2
    }
  },
  "metadata": {
    "fingerprintHash": "abc123def456",
    "previousSignups": 3
  },
  "signals": ["device_reuse", "device_seen_3_times"]
}
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pass
boolean
false if device has been used for 3+ signups, true otherwise
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latency
number
Check execution time in milliseconds
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metadata.fingerprintHash
string
Unique device fingerprint hash
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metadata.previousSignups
number
Number of previous signups from this device

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Configuration

FLAG

Recommended to FLAG device reuse since multiple accounts may be legitimate (family devices).

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Next Steps

IP Reputation

Detect VPNs and fraud

Alias Detection

Detect email aliases