Free website inspector BETA

See the tracking and tech behind any website.

Q: How can TagSpy see a website's GA4 settings without access to its Google Analytics account?

Google compiles a GA4 property's tag settings into the gtag.js file it serves to every visitor, and Tag Manager does the same with a published container in gtm.js. TagSpy downloads those public files, decodes the configuration inside them as data, and turns it into a readable report. No Google account is used.

Q: What can I type into TagSpy?

A website address, a GA4 Measurement ID (G-), a Google tag ID (GT-), a Google Tag Manager container ID (GTM-), a Meta Pixel ID or a Segment write key. For a website, TagSpy finds the IDs in the page, in first-party scripts and inside GTM containers.

TagSpy is a free website inspector. Paste a URL or a tag ID and it reads the public files a site sends to every visitor, then shows its GA4 configuration, Google Tag Manager container, Meta Pixel, Segment destinations and tech stack in a plain-language report.

Try:

No login
Nothing installed
Nothing stored

Recognises about 230 technologies, from tag managers to shaders

Google Analytics 4

Google Tag Manager

Meta Pixel

Segment

LinkedIn Insight Tag

HubSpot

Google Fonts

Cloudflare

Vercel

Next.js

React

WordPress

Shopify

Webflow

Framer

GSAP

Three.js

Tailwind CSS

01 How TagSpy sees a website

Every website has a second layer.

The page you look at is only the surface. Underneath, every site ships its scripts, its tag manager container, its analytics and pixel settings and its server headers to each visitor's browser. That layer is public. TagSpy separates it and reads it.

L1
The page you see
HTML, stylesheets, font files and design tokens: colours, type scale, breakpoints.
→ Site DNA
L2
The scripts it loads
Up to about 48 JavaScript files, including the chunks bundles reference, and any public source maps.
→ Site DNA · ID discovery
L3
The tag manager
The published GTM container from gtm.js: every tag, trigger and variable, and how they connect.
→ GTM Viewer
L4
The measurement
GA4 settings compiled into gtag/js, Meta's pixel config and Segment's published source settings.
→ GA4 · Meta Pixel · Segment
L5
The infrastructure
Hosting and CDN, response and security headers, cookies, DNS, mail records and the TLS certificate.
→ Site DNA

02 Six inspectors, one address bar

Every inspector TagSpy includes

Each report links to the others: the site you searched and the IDs found travel with you, so a GTM container leads to the GA4 property and Meta Pixel inside it. Flip a card to see everything it reveals.

/ga4

GA4 Checker

See any website's Google Analytics 4 setup without access to the account: enhanced measurement, created and modified events, key events, consent defaults and every Google tag setting.

What the GA4 Checker reveals

Library version, key events, created and modified events, cross-domain domains and unwanted referrals
Enhanced measurement per interaction, including site-search parameters
Create-event and modify-event rules with their conditions and parameter changes
Internal traffic rules, session timeout, cookie overrides, consent-mode overrides and default EEA consent
Google Signals and granular location and device restrictions by region

Open GA4 Checker

/gtm

GTM Viewer

Open any published Google Tag Manager container in a workspace modelled on GTM's own editor: tags, triggers, variables, where the data goes and a health checklist.

What the GTM Viewer reveals

Every tag with its parameters, clickable {{variable}} references and Custom HTML code
Triggers with their conditions, and which tags each one fires or blocks
Variables and everywhere they are used
Priority, sequencing, consent settings and firing options
Destinations grouped by vendor, including Custom HTML vendors like Meta Pixel and Clarity
Filters for paused, unused and untriggered tags
Download the container as a Tag Manager import file

Open GTM Viewer

/meta

Meta Pixel Checker

Find every pixel on a site or inside its GTM container, then score its signal setup and decode its codeless events into sentences.

What the Meta Pixel Checker reveals

A 0–100 signal setup score, the checks behind it and the biggest gain
Every Event Setup Tool rule, written as a sentence
Advanced matching fields, Conversions API Gateway and first-party cookies
Click IDs captured, blocked URL parameters and restricted events

Open

/segment

Segment Inspector

Enter a write key or a website and see where its customer data flows: every destination, the tracking plan and the consent rules.

What the Segment Inspector reveals

A map of site → Segment → destinations, grouped by role, with device or cloud mode
Destination IDs that link straight to their GA4, GTM and Meta reports
The tracking plan, and whether unplanned events are blocked
Consent categories and destination filters written as sentences

Open

/site

Site DNA

How any website is built: framework and version, CMS, animation libraries, 3D and shaders, typefaces, colour palette, hosting, DNS and security headers, each with the evidence behind it.

What Site DNA reveals

A one-paragraph “how it's built” summary from about 230 technology signatures
Motion: smooth scroll, scroll-driven animation, WebGL, custom shaders, page transitions and reduced-motion support
Fonts opened and read: real family name, foundry, license, glyph count and variable axes
Design tokens: palette with CSS variable names, type scale, radii, breakpoints and modern CSS in use
Hosting, CDN, TLS issuer, security headers, cookies, DNS, SPF and DMARC
Optional deep scan in headless Chromium, compare two sites side by side, and JSON download

Open Site DNA

/ai-website-detector

AI Website Detector

How likely it is that a website was built with AI, with a verdict, a confidence level, the tools it points to and every piece of evidence.

What the AI Website Detector reveals

Fingerprints of AI app builders such as Lovable, Bolt, v0, Replit Agent and Base44
Public coding-agent instruction files and commit marks from tools like Claude Code, Codex, Cursor and Copilot
Evidence in tiers, each with a likelihood ratio, combined into a score between 2% and 98%
Evidence against AI too, such as a site archived before ChatGPT
One free check per person

Open AI Detector

Numbers in the card previews are illustrative, not from a real site.

03 How it works

It reads. It never runs.

TagSpy downloads the same public files your browser receives when you visit a site, decodes the configuration inside them as data, and writes a report. No code from the site is executed and no account is needed.

Enter a site or an ID

Any website address, or a G-, GT- or GTM- ID, a Meta Pixel ID or a Segment write key.

It fetches the public files

Google's gtag/js and gtm.js, Meta's pixel config, Segment's source settings, plus the page's HTML, scripts, styles, fonts, DNS and TLS.

It decodes them into a report

Configurations are parsed as data, then written up in plain language with the evidence and exports where they help.

gtm.js — what Google publishesread-only

// A published container ships as a data object
var data = {
  "resource": {
    "version": "42",
    "macros":     [ /* variables */ ],
    "tags":       [ /* tags */ ],
    "predicates": [ /* conditions */ ],
    "rules":      [ /* triggers */ ]
  }
};
// TagSpy decodes this literal as data.
// No eval(). No browser. No login.

Simplified structure of the data object inside a Google Tag Manager gtm.js file, which TagSpy decodes without executing.

scan · northwind.shop (example)

→ resolve  northwind.shop
✓ html     200 · 3 tag IDs found in page and scripts
✓ gtm.js   GTM-NW4K2PX · 38 tags · 51 triggers · 27 variables
✓ gtag/js  G-NW7XQ21LMP · 14 events · 3 key events
✓ pixel    6 codeless rules · signal score 82/100
✓ segment  9 destinations · 4 consent gates
✓ stack    Next.js 16 · React 19 · Tailwind · GSAP · Vercel
■ report   ready · stored on server: nothing

The scan above is an illustration of a fictional store, not a real site.

04 Use cases

Who uses TagSpy, and for what

For SEO and GEO specialists

Rankings and AI citations mean little if the measurement behind them is broken. Check a site's tracking and rendering stack before you trust its numbers.

Site DNA · GA4 Checker · GTM Viewer

Audit tracking before and after a migration

Confirm the GA4 stream, key events and GTM container survived a redesign or platform move.

Check the rendering stack

See the framework, router and hosting a site uses, the context behind how search engines and AI crawlers receive its pages.

Verify referral and consent settings

Unwanted referrals, cross-domain settings and consent defaults all shape which visits, including AI-assistant referrals, get attributed.

For analysts

Audit a GA4 and GTM setup in minutes, even before a client has granted you access.

GA4 Checker · GTM Viewer

Read the real configuration

Enhanced measurement, created and modified events, key events and data redaction, as Google serves them.

Find the untidy tags

The GTM health checklist surfaces paused, unused and untriggered tags, and each row opens a filtered list.

Trace every destination

See where a container sends data, including vendors hidden inside Custom HTML tags.

For developers and designers

Learn how a site you admire is built, down to the easing library and the font's variable axes.

Site DNA · deep scan · compare

Identify the stack and versions

Framework, bundler, CSS framework, animation, smooth scroll, WebGL and shaders, each with the file and snippet as evidence.

Read the design tokens

Palette with CSS variable names, fluid type, radii, breakpoints and which modern CSS features are in use.

Compare two sites

Put two recipes side by side: stack diff, motion signals, typefaces and palettes.

For agencies and consultants

Walk into a pitch already knowing how a prospect measures, and what they're missing.

All six inspectors

Pre-sales audits in minutes

One address gives you the tracking, pixel quality score and stack to open the conversation.

Rebuild from a working container

Download a published GTM container as an import file to start a clean workspace from it.

Show the biggest gain

The Meta signal score names the single change that would lift it the most.

For competitor research

Every competitor publishes its measurement choices to anyone who looks. TagSpy makes them readable.

GTM Viewer · Segment Inspector · Meta Pixel

See which ad platforms they feed

Pixels, Segment destinations and vendor tags show where a competitor's conversion data goes.

Learn what they count as a conversion

Key events and codeless pixel rules show which actions a business values.

Spot the build choices

CMS, framework, hosting and whether the site was likely built with an AI tool.

05 Reference

TagSpy at a glance

Key facts

What: A free website inspector for tracking, tags and tech stack
Status: Public beta
Price: Free, no account. The AI Website Detector allows one free check per person.
Input: A URL, or a G-, GT-, GTM-, Meta Pixel ID or Segment write key
Reads: Only public responses, parsed as data and never executed
Stores: Nothing about the sites you check
Built by: Jayant Solanki, AI-ready SEO strategist
Open it: tag-spy.vercel.app

Tag IDs TagSpy understands

ID	What it is	Opens
`G-XXXXXXXXXX`	GA4 Measurement ID for one web data stream	GA4 Checker
`GT-XXXXXXX`	Google tag ID that can route to several destinations	GA4 Checker
`GTM-XXXXXXX`	Google Tag Manager container ID	GTM Viewer
`1480271234567890`	Meta Pixel (dataset) ID, usually 15–16 digits	Meta Pixel Checker
`k9QxW2…`	Segment write key for one source	Segment Inspector
`example.com`	Any website; its IDs are discovered for you	Site DNA and all others

TagSpy compared with other ways to check a site's tags

Capability	TagSpy	Tech-detection browser extensions	Tag debugging / preview mode	Reading files in DevTools
Install needed	No	Extension	Varies	No
Works on sites you don't manage	Yes	Yes	Partly: GTM preview needs container access	Yes
Full GTM container: tags, triggers, variables	Yes	Presence only	With access	Minified, by hand
GA4 settings: events, key events, consent	Yes	No	Hits you trigger	By hand
Meta Pixel codeless rules decoded	Yes	No	No	By hand
Tech stack with versions and evidence	Yes	Yes	No	By hand
Export container as GTM import file	Yes	No	No	No

06 Privacy

What you check stays yours.

A TagSpy report exists only in the response to the person who asked for it. Nothing is cached on the server and nothing about the sites you check is written to a database.

Your searches live in the tab's session storage, which the browser clears when you close it.
Cancelling a scan stops it on the server too.
The only rows written are rate-limit counters, deleted after 48 hours.

07 FAQ

Questions about TagSpy

What is TagSpy?

TagSpy is a free website inspector built by Jayant Solanki. Enter a website address or a tag ID and it shows the site's GA4 configuration, Google Tag Manager container, Meta Pixel setup, Segment destinations, technology stack, fonts and infrastructure, and how likely it is that the site was built with AI. It reads only public files and needs no login.

Is TagSpy free?

Yes. Every inspector is free and needs no account. The AI Website Detector includes one free check per person, because each check runs a real browser in the cloud. History and change alerts are planned as a paid feature and are not switched on yet.

How can TagSpy see a website's GA4 settings without access to its Google Analytics account?

Google compiles a GA4 property's tag settings into the gtag.js file it serves to every visitor, and Tag Manager does the same with a published container in gtm.js. TagSpy downloads those public files, decodes the configuration inside them as data, and turns it into a readable report. No Google account is used.

Is it legal to inspect another website's tags?

TagSpy reads only what a website already sends to every visitor: its HTML, its JavaScript and the tag configurations that Google, Meta and Segment serve publicly. It does not log in, bypass access controls or read private data.

Can I download another site's GTM container?

Yes. The GTM Viewer can download a published container as a Tag Manager import file (exportFormatVersion: 2). Paused tags carry no parameters and custom-template tags are skipped, because Google does not publish them.

Does TagSpy store the websites I check?

No. A report exists only in the response to you and in your browser tab's session storage, which the browser clears when the tab closes. Nothing is cached on the server. The only rows written are rate-limit counters, which are deleted after 48 hours.

What can I type into TagSpy?

A website address, a GA4 Measurement ID (G-), a Google tag ID (GT-), a Google Tag Manager container ID (GTM-), a Meta Pixel ID or a Segment write key. For a website, TagSpy finds the IDs in the page, in first-party scripts and inside GTM containers.

How does TagSpy detect a website's tech stack and fonts?

Site DNA reads the page's HTML, response headers, up to about 48 JavaScript files, stylesheets, font files, public source maps, DNS and TLS certificate, and matches them against about 230 technology signatures. Each finding shows a version when one is visible, a confidence level and the evidence. Font files are opened to read the real family name, foundry, license and variable axes.

An optional deep scan renders the page in headless Chromium to add exact library versions from live globals, WebGL details, the tested reduced-motion result and lab Web Vitals.

How does the AI Website Detector decide if a site was built with AI?

It collects evidence in tiers, strongest first: named builder traces, public agent instruction files and repository commits, template leftovers, AI coding habits, unfinished generated content and design defaults. Each item has a likelihood ratio, the ratios combine from a 15% prior, and the result stays between 2% and 98%. Evidence against AI, such as a site archived before ChatGPT, lowers the score.

How is TagSpy different from a browser technology-detection extension?

Detection extensions report which technologies are present. TagSpy also decodes how the tracking is configured: every tag, trigger and variable in a GTM container, GA4 event rules and key events, Meta Pixel codeless events and Segment destinations. It runs in any browser with nothing to install.

Who built TagSpy?

TagSpy was designed and built by Jayant Solanki, an AI-ready SEO strategist and marketing technologist based in India. It is in public beta, and feedback shapes what ships next.

Every website is already telling you how it's built.

Open TagSpy, type an address and read the second layer. It's free, it's in beta, and it takes about as long as this sentence.

Open TagSpy, it's free

Built by Jayant SolankiAI-ready SEO strategist and marketing technologist. TagSpy grew out of years of auditing GA4 and GTM setups by hand. See the portfolio or try Marketer Companion.

Last updated 26 September 2026