Internet has no shortage of fingerprinting libraries. However, only a handful free ones are note-worthy.

Free doesn't always mean the same for everyone.

1. ThumbmarkJS

ThumbmarkJS is MIT licensed, making it free to use for also commercial purposes. It is actively maintained. While being the most fresh on this list, it already has 691 stars on GitHub and keeps improving monthly.

With dozens of high-quality entropy sources, the open-source library has a 90% uniqueness, which beats all other truly free solutions.

ThumbmarkJS is small, only 20kB (NPM) and lightning fast.

If you're after a truly free, high-grade browser fingerprinting library, ThumbmarkJS is your best choice.

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2. FingerprintJS

FingerprintJS is BSL licensed, which means it is source-available and free for testing and development - not for production or commercial use.

FingerprintJS is slightly larger, with a 39 kB footprint (NPM). The client library claims a 40% - 60% accuracy.

FingerprintJS is robust and backed by a large corporation, but lower accuracy and non-permissive license drop FingerprintJS to second place.

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3. get-browser-fingerprint

For a simple use-case the get-browser-fingerprint is a microscopicly brilliant solution. It's only 10kB of size (NPM) and could not be faster.

get-browser-fingerprint has 144 stars on GitHub, and the last release was in September 2024.

The challenge with this library is with not having any indications of uniqueness and a simple incognito mode will change the fingerprint.

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4. ClientJS

Surprisingly, even after 4 years since the last commit to this GitHub project, ClientJS still is quite popular, with over 30,000 weekly installs on NPM.

ClientJS is about 55kB, so not too big, but since it hasn't been updated for a while, it performs poorly in the field. The issues are stacking up too.

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Other note-worthy projects

CreepJS

CreepJS is a high-quality project that explores and exposes different methods for browser fingerprinting. However due to its size, it is not meant as a solution for real-time fingerprinting.

CreepJS has over 2k stars on GitHub but it's not meant for production.

Supercookie

While an interesting project, I wouldn't recommend Supercookie for a fingerprinting solution. Supercookie exploits a common favicon vulnerability of browsers in a fairly intrusive manner.

It has over 4k stars on GitHub, but is not in active development.