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Overview

This tutorial walks through implementing Fingerprint to enforce paywalls, ensuring that visitors cannot bypass limits or access premium content by clearing cookies, changing IP addresses, or using incognito mode. You’ll begin with a starter app that includes a mock news site with sample articles and a basic paywall flow that limits the number of articles you can read for free. From there, you’ll add the Fingerprint JavaScript agent to identify each visitor and use server-side logic with Fingerprint data to track article views and block further access once the limit is reached. By the end, you’ll have a sample app that reliably enforces paywall limits per visitor and can be customized to fit your subscription or content access model. This tutorial uses just plain JavaScript and a Node server with SQLite on the back end. For language- or framework-specific setups, see our quickstarts.
Estimated time: < 15 minutes

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Prerequisites

Before you begin, make sure you have the following:
  • A copy of the starter repository (clone with Git or download as a ZIP)
  • Node.js (v20 or later) and npm installed
  • Your favorite code editor
  • Basic knowledge of JavaScript

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1. Create a Fingerprint account and get your API keys

  1. Sign up for a free Fingerprint trial, or log in if you already have an account.
  2. After signing in, go to the API keys page in the dashboard.
  3. Save your public API key, which you’ll use to initialize the Fingerprint JavaScript agent.
  4. Create and securely store a secret API key for your server. Never expose it on the client side. You’ll use this key on the backend to retrieve full visitor information through the Fingerprint Server API.

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2. Set up your project

  1. Clone or download the starter repository and open it in your editor.
Terminal
git clone https://github.com/fingerprintjs/use-case-tutorials.git
  1. This tutorial will be using the paywall folder. The project is organized as follows:
Project structure
.
├── public/
│   ├── article.html   # Individual article page
│   ├── article.js     # Front-end logic to display articles
│   ├── index.html     # News homepage with article list
│   └── index.js       # Front-end logic to display article summaries
├── server/
│   ├── articlesApi.js # Paywall and article-serving logic
│   ├── db.js          # Initializes SQLite and exports a database connection
│   └── server.js      # Serves static files and article endpoints
└── .env.example       # Example environment variables
  1. Install dependencies:
Terminal
npm install
  1. Copy or rename .env.example to .env, then add your Fingerprint API keys:
Terminal
FP_PUBLIC_API_KEY=your-public-key
FP_SECRET_API_KEY=your-secret-key
  1. Start the server:
Terminal
npm run dev
  1. Visit http://localhost:3000 to view the mock news homepage. Click three different articles to read them. Notice that you cannot read any new articles after that.
  2. The demo stores articles read data in localStorage to enforce the paywall. To reset the demo, either click Reset demo at the bottom of the page or manually clear the browser storage (e.g., open DevTools → Application → Local Storage → delete the site entry, or run localStorage.clear() in the console), then reload and read more articles. You’ll see the paywall is easily bypassed when client-side storage is cleared.

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3. Add Fingerprint to the front end

In this step, you’ll load the Fingerprint client when the page loads and trigger identification when the user goes to read an article. The Fingerprint client returns both a visitorId and a requestId. The visitor ID can be used to identify a browser or device uniquely and can be used to enforce the paywall. Instead of relying on the visitorId returned on the client side directly, you’ll send the requestId to your server along with the request for the article content. The server will then call the Fingerprint Events API to securely retrieve the full identification details, including the visitor ID, bot detection, and other signals.
  1. Before adding any new code, let’s delete all the client-side paywall logic and localStorage tracking. Specifically, open the public/article.js file and remove the FREE_ARTICLES_LIMIT constant and these functions: getArticlesRead(), updateFreeCount(), and updateArticlesRead().
  2. In getArticle(), delete the block that checks the number of articles read and toggles the paywall. Keep only the line that gets the articleId and everything after the fetch call.
public/article.js
async function getArticle() {
  const articleId = window.location.pathname.split("/").pop();

  try {
    const response = await fetch(`/api/article/${articleId}`);

    const data = await response.json();
    const article = data.article;

  // ...
}
  1. At the bottom of the file, remove the calls to updateArticlesRead() and updateFreeCount(), leaving only the getArticle() call.
  2. Now we’re ready to bring in Fingerprint. At the top of public/article.js, load the Fingerprint JavaScript agent:
public/article.js
const fpPromise = import(
  `https://fpjscdn.net/v3/${window.FP_PUBLIC_API_KEY}`
).then((FingerprintJS) => FingerprintJS.load({ region: "us" }));
  1. Make sure to change region to match your workspace region (e.g., eu for Europe, ap for Asia, us for Global (default)).
  2. Inside the getArticle() function, request visitor identification from Fingerprint using the get() method. Then, update the fetch call to use a POST request and include the returned requestId in the body when sending the article request to the server. (A matching POST endpoint is already set up for this tutorial.)
public/article.js
async function getArticle() {
  const articleId = window.location.pathname.split("/").pop();

  try {
    const fp = await fpPromise;
    const { requestId } = await fp.get();

    const response = await fetch(`/api/article/${articleId}`, {
      method: "POST",
      headers: { "Content-Type": "application/json" },
      body: JSON.stringify({ requestId }),
    });
    const data = await response.json();

    // ...
}
The get() method sends signals collected from the browser to Fingerprint servers, where they are analyzed to identify the visitor. The returned requestId acts as a reference to this specific identification event, which your server can later use to fetch the full visitor details. For lower latency in production, check out our documentation on using Sealed Client Results to return full identification details as an encrypted payload from the get() method.
  1. Update the “free articles remaining” message using the value returned from the server. (This won’t work yet — we’ll connect it in the next steps.)
public/article.js
async function getArticle() {
  // ...

    const data = await response.json();

    const articlesRemaining = data.articlesRemaining;
    let text = `${articlesRemaining} free articles remaining`;
    if (articlesRemaining == 0)
      text = "You have reached your free article limit";
    freeCountEl.textContent = text;

    if (!data.success) { ... }

  // ...
}

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4. Receive and use the request ID to get visitor insights

Next, pass the requestId through to your back-end logic, initialize the Fingerprint Server API client, and fetch the full visitor identification event so you can access the trusted visitorId and Smart Signals.
  1. In the back end, the server/server.js file already defines API routes for the app. Update the /api/article/:id POST route to also extract requestId from the request body and pass it into the getArticle function. (You can delete the /api/article/:id GET route.)
server/server.js
app.post("/api/article/:id", async (req, reply) => {
  const article = await getArticle(req.params.id, req.body.requestId);
  return reply.send(article);
});
  1. The server/articlesApi.js file contains the logic for fetching articles. Start by importing and initializing the Fingerprint Server API client there, and load your environment variables with dotenv.
server/articlesApi.js
import fs from "fs";
import { db } from "./db.js";
import { config } from "dotenv";
import {
  FingerprintJsServerApiClient,
  Region,
} from "@fingerprintjs/fingerprintjs-pro-server-api";

config();

const fpServerApiClient = new FingerprintJsServerApiClient({
  apiKey: process.env.FP_SECRET_API_KEY,
  region: Region.Global,
});
  1. Make sure to change region to match your workspace region (e.g., EU for Europe, AP for Asia, Global for Global (default)).
  2. Update the getArticle function to also accept requestId and use it to fetch the full identification event details from Fingerprint:
server/articlesApi.js
export async function getArticle(articleId, requestId) {
  const event = await fpServerApiClient.getEvent(requestId);

  // Simple article retrieval for demo
  const articles = JSON.parse(
    fs.readFileSync("./server/data/articles.json", "utf-8")
  );

  const article = articles.find((a) => a.id === Number(articleId));

  // ...
}
Using the requestId, the Fingerprint server client will retrieve the full data for the visitor identification request. The returned object will contain the visitor ID, IP address, device, and browser details, and Smart Signals like bot detection, browser tampering detection, VPN detection, and more. You can see a full example of the event structure and test it with your own device in our demo playground. For additional checks to ensure the validity of the data coming from your front end, view how to protect from client-side tampering and replay attacks in our documentation.

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5. Enforce paywall limits by visitor ID

Next, use the trusted visitorId to see how many free articles a visitor has read and enforce paywall limits. This ensures that even if someone clears cookies, uses incognito mode, or switches networks, their access is still tied to the same browser or device. Note: The starter app includes a SQLite database with the following table already created for you:
SQLite database tables
articles_read - Stores which articles each visitor has accessed
  id INTEGER PRIMARY KEY AUTOINCREMENT,
  visitorId TEXT NOT NULL,
  articleId TEXT NOT NULL,
  createdAt INTEGER NOT NULL
  1. Add some helper functions to the bottom of the server/articlesApi.js file to record and check articles read by the visitor:
server/articlesApi.js
// Record an article view (only if it hasn't been read before)
function recordArticleRead(visitorId, articleId) {
  const exists = db
    .prepare(
      `SELECT 1 FROM articles_read WHERE visitorId = ? AND articleId = ? LIMIT 1`
    )
    .get(visitorId, articleId);

  if (!exists) {
    db.prepare(
      `INSERT INTO articles_read (visitorId, articleId, createdAt) VALUES (?, ?, ?)`
    ).run(visitorId, articleId, Date.now());
  }
}

// Get all unique articles read by a visitor
function getArticlesRead(visitorId) {
  const rows = db
    .prepare(
      `SELECT DISTINCT articleId 
       FROM articles_read 
       WHERE visitorId = ? 
       ORDER BY createdAt ASC`
    )
    .all(visitorId);
  return rows.map((r) => r.articleId);
}
  1. Update getArticle to retrieve the visitorId, from the event object and use it to determine how many articles the visitor has read using getArticlesRead. Make sure to include articlesRemaining in the responses as well:
server/articlesApi.js
export async function getArticle(articleId, requestId) {
  const FREE_ARTICLES_LIMIT = 3;

  const event = await fpServerApiClient.getEvent(requestId);
  const visitorId = event.products?.identification?.data?.visitorId || "";

  const articlesRead = getArticlesRead(visitorId);
  const articlesRemaining = Math.max(
    0,
    FREE_ARTICLES_LIMIT - articlesRead.length
  );

  // Simple article retrieval for demo
  const articles = JSON.parse(
    fs.readFileSync("./server/data/articles.json", "utf-8")
  );
  const article = articles.find((a) => a.id === Number(articleId));
  if (!article) {
    console.error("Article not found");
    return {
      success: false,
      message: "Article not found",
      articlesRemaining,
    };
  }

  // ...
}
  1. Then add new paywall logic to check if the visitor can read the article. If so, log the article as being read and return its contents, otherwise block the article request:
server/articlesApi.js
export async function getArticle(articleId, requestId) {
  // ...

  if (!article) {
    console.error("Article not found");
    return {
      success: false,
      message: "Article not found",
      articlesRemaining,
    };
  }

  // Paywall check
  if (articlesRemaining <= 0 && !articlesRead.includes(articleId)) {
    console.error("No more free articles.");
    return {
      success: false,
      message:
        "You have reached the maximum number of free articles. Subscribe today!",
      articlesRemaining,
    };
  }

  // Record read and return updated remaining count
  recordArticleRead(visitorId, articleId);
  return {
    success: true,
    article,
    articlesRemaining: Math.max(0, articlesRemaining - 1),
  };
}

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6. Block bots and suspicious devices

This optional step uses the Bot Detection and Suspect Score Smart Signals, which are only available on paid plans.
A simple but effective way to protect your paywalled content is to block automated scraping attempts. The event object also includes the Bot Detection Smart Signal, which identifies automated activity so you can prevent bots from accessing your articles. This signal returns good for known bots like search engines, bad for automation tools, headless browsers, or other signs of scraping, and notDetected when no bot activity is found.
  1. Continuing in the getArticle function in server/articlesApi.js, check the bot signal in the event object and block requests from bots:
server/articlesApi.js
export async function getArticle(articleId, requestId) {
  // ...

  if (!article) { ... }

  // Check for bot activity
  const botDetected = event.products?.botd?.data?.bot?.result !== "notDetected";
  if (botDetected) {
    console.error("Bot detected.");
    return {
      success: false,
      message: "Article not found.",
      articlesRemaining,
    };
  }

  // ...
}
You can also add Suspect Score as an additional layer. The Suspect Score is a weighted representation of all Smart Signals in the identification payload, helping to identify suspicious activity. While you wouldn’t normally block article views based only on a high score, you could use it to flag suspicious visitors, limit access, or trigger additional verification.
  1. Below the bot detection check, add a condition that reads the Suspect Score from the event object and blocks the article request if it exceeds a chosen threshold (for example, 20):
server/articlesApi.js
export async function getArticle(articleId, requestId) {
  // ...

  // Check for bot activity
  const botDetected = event.products?.botd?.data?.bot?.result !== "notDetected";
  if (botDetected) {
    console.error("Bot detected.");
    return {
      success: false,
      message: "Article not found.",
      articlesRemaining,
    };
  }

  // Check for a high suspect score
  const suspectScore = event.products?.suspectScore?.data?.result || 0;
  if (suspectScore > 20) {
    console.error(`High Suspect Score detected: ${suspectScore}`);
    return {
      success: false,
      message: "Article not found.",
      articlesRemaining,
    };
  }

  // ...
}
Together with the visitor ID and bot detection Smart Signal, Fingerprint allows you to protect your content and enforce paywalls that can’t be bypassed with cookies or incognito mode. You can extend this by analyzing additional signals, adjusting access limits, or customizing how you handle suspicious visitors.
This is a minimal example to show how to implement Fingerprint. In a real application, make sure to apply proper security practices, error handling, and paywall logic that align with your production standards.

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7. Test your implementation

Now that everything is wired up, you can test the full protected paywall flow.
  1. Start your server if it isn’t already running and open http://localhost:3000:
Terminal
npm run dev
  1. Read three different articles and on your fourth unique article you should hit the paywall.
  2. Open a private browser window, visit the site, and try to read another new article beyond the limit. You will still be paywalled.
  3. Bonus: Test the flow using a headless browser or automation tool to see bot detection in action. A sample script is available in test-bot.js. While your app is running, run the script with node test-bot.js in your terminal and observe that the automated article requests are denied.
Terminal
node test-bot.js

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Next steps

You now have a working paywall flow that enforces article limits and blocks scraping bots with Fingerprint. From here, you can expand the logic with more Smart Signals, fine-tune access rules based on your content strategy, or add extra defenses like rate limiting or dynamic content gating. To dive deeper, explore our other use case tutorials for more step-by-step examples. Check out these related resources: