Browser fingerprinting collects a set of attributes from a user's browser and device - screen resolution, installed fonts, plugins, timezone, language settings, GPU information, and more - and combines them into a profile that can uniquely identify the user.
Unlike cookies, which are stored explicitly and can be deleted or blocked by the user, a fingerprint is assembled from information the browser transmits during normal web requests. The user is tracked without any visible indicator. According to the EFF's Panopticlick project, browser fingerprints are unique 83.6% of the time, meaning the vast majority of users can be individually identified.
Key components of a fingerprint include the User-Agent string, screen resolution and color depth, timezone and language settings, installed plugins and fonts, Canvas fingerprint (a hash of an image drawn via the Canvas API), WebGL fingerprint (GPU rendering characteristics), and AudioContext fingerprint (audio processing traits).
For URL shortening services, fingerprinting can supplement click analytics in environments where cookies are unavailable - private browsing mode, browsers that block third-party cookies, and so on. However, GDPR and the ePrivacy Directive treat fingerprinting the same as cookies for consent purposes, so compliance is essential.
Browser vendors are pushing back. Firefox's Enhanced Tracking Protection blocks known fingerprinting scripts. Safari's Intelligent Tracking Prevention degrades fingerprint accuracy. Brave randomizes fingerprint data entirely. You can find related books on Amazon.