Client-Side Scripts

Impressio's client-side layer consists of 4 JavaScript engines that are concatenated and served as a single bundle (h.js) via Lambda@Edge. Each engine is self-contained, uses IIFE pattern, and communicates through window globals.

How it works: When a page loads h.js, Lambda@Edge dynamically concatenates all 4 scripts into a single response, injecting server context (CloudFront headers, JA4 fingerprint, ASN) as a JSON placeholder that the fingerprint engine reads at runtime.

🔐 Fingerprint Engine

v4.5.2 · 589 LOC

Adaptive hybrid fingerprinting combining server-side signals (JA4, ASN, timezone) with client-side techniques (Canvas, WebGL, AudioContext, fonts, WebRTC). Privacy-aware: adapts strategy based on cookie policy.

window.h

📡 Tracking Engine

v5.0.0 · 982 LOC

Core tracking with identity resolution, domainprint sync, IndexedDB attribution persistence, custom events API, and native app support. Orchestrates all other engines.

window.impressio

🎯 Campaign Detector

v1.0.0 · 1,479 LOC

Detects and normalizes campaign parameters from 60+ platforms. Resolves unexpanded macros, identifies platforms via click IDs, UTM sources, and user-agent patterns.

window.TrafficCampaign

🧠 Behavioral Biometrics

v2.1.0 · 395 LOC

Human behavior pattern analysis generating ~165 bits of entropy from mouse movements, keyboard rhythm, scroll patterns, and touch interactions.

window.__behavioralV2

Execution Order

Order	Script	Timing	Dependencies
`1`	fingerprint.js	Immediate (IIFE)	None — runs first
`2`	behavioral_v2.js	Immediate (IIFE)	None — registers API on window
`3`	campaign.js	Immediate (IIFE)	None — self-contained
`4`	tracking.js	DOMContentLoaded	`window.h`, `window.__behavioralV2`

Data Flow

Browser loads h.js (Lambda@Edge concatenated bundle)
  │
  ├─ fingerprint.js → generates hybrid hash → window.h / window.__fpDebug
  ├─ behavioral_v2.js → registers collectors → window.__behavioralV2
  ├─ campaign.js → detects campaign/source → window.TrafficCampaign
  │
  └─ tracking.js (DOMContentLoaded)
       ├─ captureAttribution() → IndexedDB touchpoints
       ├─ capturePageView() → IndexedDB pageview
       ├─ loadAttrCache() → window.__impressioAttrCache
       ├─ getDomainprint() → cookie __dp / POST /t
       ├─ window.h.generateStable() → fingerprint
       ├─ sendTrackingEvent() → POST /t (main payload)
       ├─ __behavioralV2.start() → 6s collection
       └─ sendBehavioralData() → POST /t (behavioral payload)

Installation

The scripts are served automatically when you add the Impressio tracking snippet to your page. No manual installation is needed — Lambda@Edge handles bundling and delivery.

<!-- Standard installation -->
<script src="https://t.getimpress.io/h.js" 
        data-user-id="YOUR_USER_ID"
        data-organization-id="YOUR_ORG_ID"
        data-debug="false"
        async></script>

Debug mode: Add data-debug="true" to enable console logging for all 4 engines. All log prefixes are bracketed: [FP], [Tracking],[BehavioralV2], [Campaign].