Introduction to ThumbmarkJS
What is ThumbmarkJS
ThumbmarkJS is the best and most popular free browser fingerprinting library. It can be used to generate a highly distinct digital fingerprint of the browser to identify users without cookies. This digital fingerprint stays the same even when cache is cleared, or if incognito is used.
The free, open source library is MIT-licensed. For drastically improved fingerprinting, you can use the API as well. There are free and paid options for the API.
ThumbmarkJS is already used by companies such as Google, Facebook and Cloudflare, and a total of over 60,000 sites monthly use ThumbmarkJS to identify their visitors. Each month more than 1 billion thumbmarks are created.
Relevant links:
Different types of implementations
You can use ThumbmarkJS in many ways, e.g. directly importing it in the browser using javascript, or by installing it into your node project.
ThumbmarkJS can be used without the backend, but for projects that require higher uniqueness of the thumbmarks, the API key is required.
The API key can be obtained from thumbmarkjs.com
For a simple import with javascript, check out this page
For framework integrations, see the dedicated guides:
Uniqueness
The open source library produces a fingerprint that is unique enough for many use cases on its own.
Using the API significantly improves uniqueness on top of that, because the backend incorporates server-side signals (HTTP headers, TLS handshake, IP-derived data) that the client cannot see, and reconciles them against historical data.
Mileage varies, and it depends on your audience.