OpenClientID | Open source fingerprinting

Open-source browser and device fingerprinting for fraud prevention

OpenClientID combines browser, device, network, and server signals into a composite fingerprint for anti-fraud and customer tracking, without relying on a brittle single hash.

Your composite fingerprint

-fingerprint

-slice

Visitor identity

Hello, Unavailable

Visits: UnavailableLast seen: UnavailableStatus: Unavailable

Derived from component

Loading browser and device signals...

Raw component value

Loading component value...

Easy to get started

Add OpenClientID in minutes and start collecting fingerprinting signals immediately.

bun add openclientid

Initialize fingerprint

const fp = await getFingerprint()

Server-side fingerprinting

OpenClientID fingerprints server and network signals in addition to browser and device signals. That includes JA4 , IP addresses, and other server-side indicators. You can self-host the full stack, or sign up and use the managed cloud platform.

Your IP

Unavailable

Your JA4

Unavailable

Client risk

Server risk

Combined risk

Disclaimer: "JA4" is a trademark of FoxIO.

Key features

Composite fingerprints for partial matching

Partial matches help you identify returning users even when the full fingerprint changes.

Fully open source & fully self-hostable

Includes a fingerprinting backend written in Rust.

Extendable & customizable

Want to fingerprint more signals? Add your own components.

We fingerprint a lot

Covers everything ThumbmarkJS and FingerprintJS do (and more).

Pricing

Use OpenClientID however you want: fully free and self-hosted, or managed in the cloud.

Open source and free forever

The OpenClientID library is free to use with unlimited local fingerprints. You can self-host server fingerprinting yourself at no license cost.

Managed cloud is optional

Cloud plans are for hosted infrastructure, team workflows, and managed billing. Use them only if you prefer not to operate the stack yourself.

Free

For prototyping and early experiments.

€0/month

Included5,000 calls

OverageHard block

Start free

Starter

For teams shipping their first integration.

€9/month

Included50,000 calls

Overage€0.50 / 1k calls

Move to Starter

Pro

For production traffic and analytics.

€49/month

Included500,000 calls

Overage€0.30 / 1k calls

Scale with Pro

Enterprise

Custom limits, deployment, and support.

Custom

IncludedCustom

OverageVolume discount

Talk to us

One changed signal should not break identity

User adds a new preferred browser language.

Accept-Language updates from en-US to en-US,de-DE.

FingerprintJS-style single hash

Before

9f3b7b1c5d2e4f80a6c9d7e1

After one signal changes

c5d2e4f8aa6c9d7e14c1d8a9

Match result: no match

Small browser changes produce a new full hash, so this session looks like a different visitor.

OpenClientID composite matching

Before

-fingerprint

-slice

After one signal changes

newsegment

-fingerprint

-slice

Match result: partial match

Only one component changes. The remaining components keep the visitor linked to the same identity.

What we fingerprint

Signals span browser, device, network, rendering, storage, performance, and infrastructure layers.

User agentBrowser versionPlatformLanguageTimezoneScreen resolutionColor depthCPU coresDevice memoryTouch pointsCanvas outputWebGL rendererAudio contextFont metricsInstalled fontsDo Not TrackCookie supportLocal storageSession storageIndexedDB behaviorWebRTC hintsMedia devicesBattery API hintsPerformance timingNetwork RTT hintsTLS fingerprint (JA4)IP address patternsASN / network metadataHeader orderAccept-* headersConnection hintsProxy indicatorsServer TLS detailsRequest cadenceOS fingerprint signalsBrowser feature flagsUser agentBrowser versionPlatformLanguageTimezoneScreen resolutionColor depthCPU coresDevice memoryTouch pointsCanvas outputWebGL rendererAudio contextFont metricsInstalled fontsDo Not TrackCookie supportLocal storageSession storageIndexedDB behaviorWebRTC hintsMedia devicesBattery API hintsPerformance timingNetwork RTT hintsTLS fingerprint (JA4)IP address patternsASN / network metadataHeader orderAccept-* headersConnection hintsProxy indicatorsServer TLS detailsRequest cadenceOS fingerprint signalsBrowser feature flags

Evidence-backed comparison

ThumbmarkJS vs FingerprintJS vs OpenClientID

All non-`TODO` claims are mapped to local repository evidence paths. Fingerprint factor support below compares OSS client registries.

Feature comparison

Open-source client

ThumbmarkJSSupported

FingerprintJSSupported

OpenClientIDSupported

Open-source backend

ThumbmarkJSNot included

FingerprintJSNot included

OpenClientIDSupported

Full-stack self-hosting (client + backend)

ThumbmarkJSNot included

FingerprintJSNot included

OpenClientIDSupported

Composite matching

ThumbmarkJSTODO: verify

FingerprintJSTODO: verify

OpenClientIDSupported

Server-side signals

ThumbmarkJSTODO: verify

FingerprintJSTODO: verify

OpenClientIDSupported

Extensibility

ThumbmarkJSSupported

FingerprintJSSupported

OpenClientIDSupported

Managed cloud optional

ThumbmarkJSTODO: verify

FingerprintJSSupported

OpenClientIDSupported

Identifier model

ThumbmarkJSSupported

FingerprintJSTODO: verify

OpenClientIDSupported

Total supported fingerprinting factors

ThumbmarkJS32

FingerprintJS46

OpenClientID58

Feature	ThumbmarkJS	FingerprintJS	OpenClientID
Open-source client	Supported MIT-licensed open-source browser client.	Supported MIT-licensed open-source browser fingerprinting library.	Supported Open-source JS client package in the OpenClientID project.
Open-source backend	Not included Managed API integration exists, but backend source code is not publicly available.	Not included FingerprintJS OSS is client-side; Fingerprint Identification backend is closed-source.	Supported Rust backend source is available
Full-stack self-hosting (client + backend)	Not included OSS client bundles are hostable, but backend/API implementation is not open-source.	Not included FingerprintJS OSS client can be self-hosted, but Fingerprint Identification backend is closed-source.	Supported Server README includes local run + Docker self-hosting for the full stack.
Composite matching	TODO: verify Client returns a single `thumbmark` hash; API matching internals are not open-source.	TODO: verify OSS library computes client-side hashed IDs; paid fuzzy/deduplicated matching happens in the paid closed-source service.	Supported Client builds stable/unstable composite parts and appends server hash with marker-based combined composite.
Server-side signals	TODO: verify API version advertises server-side components, but backend implementation details are not publicly available.	TODO: verify Fingerprint Identification server-side processing is closed-source.	Supported Server fingerprint includes TLS, HTTP, and IP components.
Extensibility	Supported Supports registering custom components via `includeComponent`.	Supported Documented extension workflow for adding/removing components before hashing.	Supported Component selection is configurable (`FingerprintConfig.components`) and server exposes hook-based extension points.
Managed cloud optional	TODO: verify Managed API exists, but pricing/hosting guarantees require verification.	Supported OSS library is available without paid Identification service.	Supported Pricing copy states self-hosted OSS is free and cloud is optional.
Identifier model	Supported Returns a `thumbmark` hash and can include `visitorId` from API response.	TODO: verify OSS exposes a hashed visitor identifier; paid VisitorID semantics are part of a closed-source service.	Supported Client exposes composite/stable/unstable identifiers plus server-combined composite outputs.
Total supported fingerprinting factors	32	46	58

Fingerprinting factors

Expand to view the full per-factor comparison.

Pricing comparison

Snapshot values preserve native currencies (`€`, `$`) and are shown without conversion.

Open-source client/library

ThumbmarkJS

Free

FingerprintJS

Free

OpenClientID

€0/month

Free API tier

ThumbmarkJS

Free

FingerprintJS

$0/month

OpenClientID

€0/month

Paid entry tier

ThumbmarkJS

15€ per month

FingerprintJS

$99/month

OpenClientID

€9/month

Higher paid tier

ThumbmarkJS

15€ per month

FingerprintJS

$99/month

OpenClientID

€49/month

Enterprise

ThumbmarkJS

Custom

FingerprintJS

Custom

OpenClientID

Custom

Included API calls

ThumbmarkJS

15,000

FingerprintJS

20,000

OpenClientID

50,000 calls

Additional API calls

ThumbmarkJS

€1.00 / 1,000

FingerprintJS

$4 / 1,000

OpenClientID

€0.50 / 1,000

Plan / metric	ThumbmarkJS	FingerprintJS	OpenClientID
Open-source client/library	Free	Free	€0/month
Free API tier	Free	$0/month	€0/month
Paid entry tier	15€ per month	$99/month	€9/month
Higher paid tier	15€ per month	$99/month	€49/month
Enterprise	Custom	Custom	Custom
Included API calls	15,000	20,000	50,000 calls
Additional API calls	€1.00 / 1,000	$4 / 1,000	€0.50 / 1,000