FingerprintJS is an open-source JavaScript library designed to identify browsers using browser and device characteristics. It is mainly useful for developers building websites and web applications that need visitor identification, fraud prevention, security monitoring, or user recognition without relying only on traditional cookies.
Unlike a normal cookie-based identifier, a browser fingerprint is created from characteristics available in the browser environment. FingerprintJS processes these attributes on the client side and generates a hashed visitor identifier.
For developers working with browser security, fraud detection, device identification, bot detection, and web analytics, FingerprintJS can be an interesting technology to understand.
What Is FingerprintJS?
FingerprintJS is a free and open-source browser fingerprinting library for JavaScript.
The library queries different browser attributes and combines them to calculate a visitor identifier. The official project is available under the MIT license, allowing developers to use and modify the software under the license terms.
Instead of asking a visitor to log in before every interaction, a website can use browser fingerprinting as an additional signal for recognizing whether the same browser has visited before.
How Does FingerprintJS Work?
Browser fingerprinting works by examining characteristics exposed by the browser.
Depending on the environment, fingerprinting can use signals related to the device, operating system, screen configuration, browser, fonts, canvas, audio, and other browser characteristics.
FingerprintJS processes these attributes inside the browser and generates a hashed identifier known as a visitorId. The official example shows developers loading the library and calling fp.get() to retrieve the visitor identifier.
FingerprintJS Visitor ID
The visitorId is the main result developers typically use when integrating the library.
For example, a website can use the identifier as one signal when analyzing repeated visits or suspicious activity.
It is important to understand that a visitor ID is not the same thing as a person’s real-world identity. It represents a browser/device fingerprint generated from available technical characteristics.
FingerprintJS vs Cookies
Cookies store information in the browser as data created by a website. Browser fingerprinting works differently by creating an identifier from characteristics of the browser environment.
One notable feature of FingerprintJS is that its fingerprint can remain recognizable when browser cookies and local storage are cleared, including in private browsing scenarios.
This makes browser fingerprinting technically different from traditional cookie-based tracking.
However, fingerprinting is not perfect. Changes to the browser, operating system, device configuration, privacy settings, or other signals can affect identification.
What Is FingerprintJS Used For?
FingerprintJS can be useful in several technology and security applications.
Fraud Detection
Online businesses can use device and browser signals as one part of a broader fraud-detection system.
For example, a website dealing with account creation, payments, promotions, or high-risk transactions may want additional signals to identify repeated or suspicious activity.
Fingerprinting should generally be treated as one security signal, rather than the only method used to decide whether an activity is fraudulent.
Account Abuse Prevention
Some websites need to prevent users from repeatedly creating accounts or abusing promotional offers.
A browser identifier can provide another signal for recognizing previously seen browsers.
This can be useful alongside account information, IP intelligence, behavioral signals, rate limits, and other security controls.
Bot and Automated Traffic Detection
FingerprintJS also maintains a separate open-source project called BotD, which is designed to detect basic bots and automation tools directly in the browser. BotD is available under the MIT license.
This is useful for developers who need to distinguish normal browser activity from automated traffic.
Visitor Identification
Web applications can use browser fingerprinting as an additional way to recognize returning visitors.
For example, a developer could combine a visitor identifier with other application data to understand whether repeated activity is coming from the same browser environment.
How to Install FingerprintJS
Developers can install FingerprintJS through npm.
The official project currently uses the package:
@fingerprintjs/fingerprintjs
A typical installation starts with:
npm install @fingerprintjs/fingerprintjsThe library can then be imported into a JavaScript or TypeScript application.
Basic FingerprintJS Example
A basic implementation initializes the FingerprintJS agent and requests a visitor identifier:
import FingerprintJS from '@fingerprintjs/fingerprintjs'
const fpPromise = FingerprintJS.load()
const fp = await fpPromise
const result = await fp.get()
console.log(result.visitorId)This example follows the installation and usage pattern provided in the official FingerprintJS repository.
Developers should then decide how that identifier is used within their own application and backend architecture.
FingerprintJS Open Source vs Fingerprint Pro
One of the most important things to understand is that FingerprintJS and Fingerprint Pro are not identical products.
The open-source FingerprintJS library runs on the client side. The commercial Fingerprint platform adds server-side technology and additional signals designed for higher-scale device identification and fraud-related use cases.
The open-source version is therefore useful for developers who want a free browser fingerprinting library, while businesses with more demanding identification requirements may consider a commercial device-intelligence service.
FingerprintJS Open Source
Best For: Developers, experiments, prototypes, browser fingerprinting projects, and applications that need a client-side fingerprint.
License: MIT
Processing: Primarily client-side
Main Advantage: Free and open source
Limitation: Lower accuracy and greater exposure to spoofing because the fingerprint is generated inside the browser itself.
Fingerprint Pro
Best For: Businesses requiring more advanced device identification and fraud-prevention capabilities.
Main Advantage: Server-side signals and additional identification capabilities.
Pricing: Fingerprint’s current public information lists paid plans for its commercial platform, with pricing depending on the service and usage.
For a business processing large volumes of users or high-risk transactions, the difference between a client-only library and a server-supported device intelligence platform can be significant.
Is FingerprintJS Accurate?
FingerprintJS itself states that the open-source client-side library has lower accuracy than its commercial offering.
The reason is straightforward: the open-source library generates and processes the fingerprint in the browser. This makes the system more vulnerable to spoofing and reverse engineering.
Therefore, developers should avoid treating a FingerprintJS identifier as an unchangeable identity.
For security-sensitive applications, it is better to combine fingerprinting with additional signals such as authentication, IP/network intelligence, rate limiting, behavioral analysis, and server-side verification.
Is FingerprintJS Safe and Legal?
Browser fingerprinting raises important privacy considerations because it can be used to recognize a browser across visits.
Whether and how fingerprinting can be used depends on the application’s purpose, jurisdiction, privacy requirements, disclosures, and consent obligations.
Developers should clearly understand what information they collect, why they collect it, how long it is retained, and whether applicable privacy laws require notice or consent.
FingerprintJS itself is open-source software under the MIT license, but using the library in a website does not automatically make the website’s data-collection practices compliant with every privacy law.
FingerprintJS for Fraud Prevention
Fingerprinting can be particularly valuable in applications where multiple accounts, automated abuse, or suspicious transactions are concerns.
Examples include:
- Online marketplaces
- E-commerce platforms
- Financial technology applications
- Subscription services
- Online gaming platforms
- Promotional campaigns
- Account registration systems
- Digital advertising platforms
The strongest implementations generally combine several signals rather than relying on browser fingerprinting alone.
FingerprintJS Limitations
FingerprintJS is useful, but it is not a perfect identity system.
Browser Changes
Changing browsers, updating software, modifying device settings, or using privacy tools can affect fingerprint signals.
Spoofing
Because the open-source fingerprint is generated on the client, sophisticated users or automated systems may attempt to manipulate browser characteristics.
Shared Devices
Multiple people can use the same computer or browser environment, so a fingerprint should not automatically be interpreted as a unique human being.
Privacy Concerns
Fingerprinting can have privacy implications because it is designed to recognize browser environments. Developers should consider applicable privacy requirements before deploying it.
FingerprintJS Alternatives
Depending on your use case, there are several alternatives to consider.
Fingerprint Pro: Suitable for businesses looking for a commercial device-intelligence platform with server-side capabilities.
BotD: Useful when the primary requirement is detecting automated browsers and bots. Fingerprint maintains BotD as a separate open-source project.
Traditional Cookies: Still useful for ordinary session management and user preferences, although they work differently from browser fingerprinting.
Server-Side Risk Detection: Businesses can also combine IP intelligence, authentication, behavioral analytics, and transaction monitoring instead of depending on one browser signal.
Get FingerprintJS
Developers can access the official FingerprintJS source code and documentation through its GitHub repository.
FingerprintJS on GitHub
The repository includes installation instructions, examples, API resources, supported browser information, and migration documentation.
Frequently Asked Questions
What is FingerprintJS used for?
FingerprintJS is used for browser fingerprinting and visitor identification. Developers can use it as an additional signal for applications involving analytics, account abuse prevention, fraud detection, and security.
Is FingerprintJS free?
Yes. The open-source FingerprintJS library is available under the MIT license. Fingerprint also offers commercial products with additional capabilities.
Is FingerprintJS a JavaScript library?
Yes. FingerprintJS is a client-side browser fingerprinting library written for the JavaScript ecosystem and distributed through npm.
Can FingerprintJS identify a person?
Not directly. FingerprintJS generates a technical browser identifier. It should not automatically be interpreted as proof of a person’s real-world identity.
Can FingerprintJS replace cookies?
Not exactly. Fingerprinting and cookies use different mechanisms and have different purposes. FingerprintJS can provide an additional browser-recognition signal, but it does not simply function as a replacement for every cookie-based feature.
Is FingerprintJS good for fraud detection?
It can be useful as one signal in a broader fraud-prevention system. The open-source client-side version has limitations, so security-sensitive applications may require additional server-side and behavioral signals.
Final Verdict
FingerprintJS is a useful technology for developers who want to understand and implement browser fingerprinting, visitor identification, and device-based security signals.
Its biggest advantage is that the open-source library is free, developer-friendly, and easy to integrate into JavaScript applications.
However, it should not be treated as a perfect or permanent identity solution. The client-side nature of the open-source library creates limitations around accuracy and spoofing.
For simple browser fingerprinting projects, FingerprintJS is a strong technology to explore. For businesses handling high-value transactions, fraud prevention, or large-scale device identification, a combination of server-side signals and specialized security technology may be more appropriate.