Registry / http-networking / express-fingerprint

express-fingerprint

library1.2.2jsnpmunverified

express-fingerprint is an Express middleware designed for passive, server-side client fingerprinting. It allows developers to identify incoming requests based on characteristics observable in HTTP request contents without executing any client-side code. The current stable version is `1.2.2`. The library processes information such as the User-Agent string, HTTP Accept headers, and GeoIP data (if available) to generate a unique hash and a detailed component breakdown for each request, accessible via `req.fingerprint`. Releases are infrequent but have recently addressed critical import issues and added TypeScript support. A key differentiator is its strict adherence to server-side data collection, prioritizing privacy by avoiding client-side scripts, and offering extensibility through custom parameter functions to gather additional request-specific data.

http-networking web-framework auth-security

npm install express-fingerprint

github ↗package ↗

INSTALL

IMPORT

SIG · EXPRESS-FINGERPRIN

express-fingerprint

http-networkingjavascriptv1.2.2

Install

—

Import

—

Disk

—

Pass rate

0/ 6

Env Coverage0 / 6

glibc

18–22

musl

18–22

Install & Compatibility

Where this runs

tested against v? · npm install

Install × environment matrix

Each cell = how many times install + import succeeded across repeated harness runs. Partial = flaky.
glibc = Debian/Ubuntu slim · musl = Alpine Linux

musl

node 18–226 runs

build_error

glibc

node 18–226 runs

build_error

Code

Verified usage

Verified import paths — ran on the pinned version, not inferred.

Fingerprint

✓ import Fingerprint from 'express-fingerprint'

✗ import { Fingerprint } from 'express-fingerprint'

Since v1.2.0, the package primarily uses a default export. Use named imports only for static properties like `Fingerprint.useragent`.

Fingerprint

✓ const Fingerprint = require('express-fingerprint')

✗ const { Fingerprint } = require('express-fingerprint')

CommonJS usage requires importing the default export directly. Fixes for this specific `require` pattern were included in v1.2.2.

Fingerprint.useragent

✓ import Fingerprint from 'express-fingerprint'; // Then use Fingerprint.useragent

Static properties like `useragent`, `acceptHeaders`, and `geoip` are accessed directly on the default `Fingerprint` export, not as named imports.

This quickstart demonstrates how to initialize `express-fingerprint` as middleware, including default and custom parameters, and how to access the generated fingerprint object on the `req` object for every incoming request.

import express from 'express'; import Fingerprint from 'express-fingerprint'; const app = express(); app.use(Fingerprint({ parameters: [ // Default parameters Fingerprint.useragent, Fingerprint.acceptHeaders, Fingerprint.geoip, // Custom additional parameters function(next) { // Example: Add a custom header value const customHeader = this.req.headers['x-custom-id'] || 'N/A'; next(null, { 'customHeaderId': customHeader }); }, function(next) { // Example: Asynchronously fetch and add data setTimeout(() => { next(null, { 'customAsyncParam': 'asyncValue' }); }, 50); } ] })); app.get('/', (req, res) => { // The fingerprint object is available on req.fingerprint console.log('Request Fingerprint:', req.fingerprint); res.json({ message: 'Fingerprint collected!', fingerprint: req.fingerprint }); }); app.listen(3000, () => { console.log('Server listening on http://localhost:3000'); });

Debug

Known issues

breakingThe `require('express-fingerprint')` statement was not working correctly in some versions prior to `1.2.2`, leading to import errors for CommonJS users.

fix

Ensure you are using version `1.2.2` or later. If upgrading, verify your `require` statements are consistent with a default export (`const Fingerprint = require('express-fingerprint')`).

affects: <1.2.2

gotchaCustom fingerprint parameters are asynchronous and require a specific callback pattern (`next(null, { key: 'value' })`). Incorrect use can prevent data from being added or halt the middleware chain.

fix

Always invoke `next(null, dataObject)` with `dataObject` containing the properties you wish to add to the fingerprint component. Ensure `dataObject` is a plain object.

affects: >=1.0.0

gotchaThe library primarily uses a default export. Attempting to destructure it as a named import in ESM (`import { Fingerprint } from 'express-fingerprint'`) or CommonJS (`const { Fingerprint } = require('express-fingerprint')`) will result in `undefined` or a `TypeError`.

fix

For ESM, use `import Fingerprint from 'express-fingerprint'`. For CommonJS, use `const Fingerprint = require('express-fingerprint')`. Static properties like `Fingerprint.useragent` are accessed directly on the default export.

affects: >=1.2.0

Errors

Common errors & fixes

TypeError: Fingerprint is not a function

Attempting to use `Fingerprint` as a constructor or function after incorrectly importing it as a named export from a default-exported module.

fix

Adjust your import statement to correctly get the default export: `import Fingerprint from 'express-fingerprint'` (ESM) or `const Fingerprint = require('express-fingerprint')` (CommonJS).

Error: Cannot find module 'express-fingerprint'

The package is either not installed, or the Node.js runtime cannot locate it due to incorrect path resolution or corrupted `node_modules`.

fix

Run `npm install express-fingerprint` to ensure the package is installed. If the error persists, clear your `node_modules` and `package-lock.json` and reinstall dependencies.

TypeError: Cannot read properties of undefined (reading 'fingerprint')

The `express-fingerprint` middleware has not been correctly applied to the Express app, or `req.fingerprint` is being accessed before the middleware has had a chance to execute.

fix

Ensure `app.use(Fingerprint(...))` is called *before* any routes or other middleware that attempt to access `req.fingerprint`. Verify there are no errors in the middleware's initialization.

Upgrade

Version history

1.2.2latest on npm

Audit

Dependencies

expressrequiredPeer dependency, required for middleware functionality.

Agent activity

20 hits · last 30 days

node

Amazon

OpenAI (training)

Resources

githubhttps://github.com/yusukeshibata/express-fingerprint ↗

packagehttps://www.npmjs.com/package/express-fingerprint ↗