Confidence & Entropy

Confidence Score

Every fingerprint includes a confidence score (0–1) that tells you how reliable the identification is.

const fp = await neoprint.get()
console.log(fp.confidence) // 0.87

Confidence is calculated from three factors:

• Coverage (30%) — How many collectors returned valid data. If 15 out of 19 succeed, coverage is 0.79.
• Stability (50%) — Average stability of successful collectors. Stable signals (math: 0.95) weigh more than volatile ones (network: 0.30).
• Entropy (20%) — Average entropy normalized to 0–1. More bits = more unique = higher confidence.

Entropy

Entropy measures how many bits of identifying information the fingerprint contains.

console.log(fp.entropy) // 94.5 bits
// 2^94.5 ≈ 19.8 septillion possible unique fingerprints

Higher entropy = more unique fingerprint = less likely to collide with another device.

When to Trust a Fingerprint

Confidence	Meaning	Action
0.8+	Strong identification	Trust the fingerprint
0.5–0.8	Moderate	Use with other signals (cookies, sessions)
< 0.5	Weak	Don't rely on fingerprint alone

Low confidence usually means:

• Many collectors failed (privacy extensions, restrictive browser)
• Browser has fingerprinting resistance enabled
• Running in a very restricted environment