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Event Watcher Event Watcher × Stack Builder

Scan Any Site. Build a Stack Diagram in Three Clicks.

Start building your Martech stack easier than before by using Rune Andersen’s Event Watcher Chrome extension. Scan what tracking scripts and pixels are on the site, export the data, and import it here. Getting started is as easy as 1, 2, 3. Thanks to Rune for adding this feature to his extension.

Install free on Chrome Open Stack Builder

Free · Open source · Made with care by Rune Andersen

Event Watcher detecting tracking platforms on a site, with Save as MartechStack Builder JSON highlighted, alongside the Stack Builder canvas

As easy as 1, 2, 3

From "I wonder what they’re running" to a working stack diagram in under a minute.

1

Install Event Watcher

Free Chrome extension. One click from the Web Store. Opens as a tab in DevTools — no signup, no telemetry.

Install from Chrome Web Store →
2

Scan + Export

Visit any site, open DevTools → Event Watcher. The extension classifies 400+ platforms in real time. Click Save as MartechStack Builder JSON.

Tag managers, pixels, analytics, CDPs, CMPs, session replay — all detected from real network signals.

3

Import into Stack Builder

In Stack Builder: File → Import JSON. Pick the file. Your stack diagram appears, vendors auto-bound to our 150+ vendor knowledge base.

Open Stack Builder →

400+ platforms recognized

Event Watcher classifies what it detects into categories that map directly to your Stack Builder canvas.

Tag Managers

GTM, Tealium iQ, Adobe Launch, Segment, Rudderstack

Analytics

GA4, Adobe Analytics, Amplitude, Mixpanel, Heap

Advertising

Meta, LinkedIn, TikTok, Google Ads, Snapchat, Pinterest

CDPs

Segment, mParticle, Tealium, RudderStack, Hightouch

Consent (CMP)

OneTrust, Cookiebot, Didomi, Usercentrics, Sourcepoint

Session Replay

FullStory, Hotjar, ContentSquare, Clarity, LogRocket

A/B Testing

Optimizely, VWO, Dynamic Yield, Adobe Target

Server-side / SDKs

Stape, Addingwell, custom collectors, server containers

Event Watcher’s recognition library is open and growing. See the full list at eventwatcher.dev.

Three ways teams use this combo

For consultants

Pre-kickoff client audits

Walk into the first meeting with a scored stack diagram already on screen. Scan the client’s site in five minutes; arrive informed.

For in-house teams

Reality-check the spreadsheet

Compare what’s actually firing on your production site against what your "tools list" says. Find the rogue pixel nobody owns.

For competitive research

Map a competitor's stack

Stack Builder + Event Watcher beats BuiltWith for Martech specifically — better classification, real architecture diagrams, no paywall.

Made by Rune Andersen

Rune is a Copenhagen-based developer building tools for Martech and analytics debugging. Event Watcher is free, open source, and actively maintained. We added the Save as MartechStack Builder JSON export at his suggestion — and we’re grateful for the partnership.

Visit eventwatcher.dev Install on Chrome

Frequently Asked Questions

What is Event Watcher?
A free Chrome DevTools extension by Rune Andersen (Copenhagen) that recognizes 400+ tracking platforms on any website — tag managers, analytics, ad pixels, CDPs, CMPs, session replay, A/B testing tools. It reads the page in real time, classifies what it sees, and lets you export the result.
Does it cost anything?
No. Event Watcher is free and open source. Stack Builder import is free too — your scan-and-import flow has zero billing friction.
What gets imported into my stack diagram?
Every detected platform becomes a vendor node, automatically categorized (data collection, analytics, advertising, governance, etc.). Where Event Watcher can infer integrations between tools — for example, GTM firing a Meta Pixel — those become edges. You land on a canvas with the basics already in place, ready to refine.
How accurate is the detection?
Event Watcher uses signal-based detection — script URLs, network endpoints, datalayer pushes, cookie names — so it catches what’s actually firing, not just what’s declared. Branded vendors auto-bind to our knowledge base for logos, capabilities, and pricing data. You can edit anything after import.
Do I need a Stack Builder account to import?
You can import the JSON anonymously and view the diagram, but saving and AI features require a free account. The Free plan supports 3 cloud saves — enough to evaluate the flow.
Will Event Watcher see private data?
It runs locally in your browser DevTools panel — no servers, no telemetry. The JSON you export contains the detected vendors and (optionally) their relationships. No cookies, no PII, no datalayer values are written to the file.
Can I use this on client sites or just my own?
Either. Consultants use it to audit client stacks before kickoff. Agencies use it to scope migration projects. In-house teams use it to verify what’s actually deployed vs. what the spreadsheet says. The extension reads only what the public browser sees.

Scan, export, import — in under a minute

Free Chrome extension + free Stack Builder account. The fastest path from a URL to a working Martech architecture diagram.

Install Event Watcher Open Stack Builder

No credit card required. Free plan available.