What information can a website collect about me without permission?

Without a single prompt, a website can read your IP address, approximate city, device type, operating system, browser and version, screen resolution, battery level, installed fonts, GPU, connected cameras and microphones, and a canvas/audio fingerprint. This page demonstrates dozens of these signals live in your own browser.

What is a browser fingerprint?

A browser fingerprint is a near-unique identifier assembled from your device's characteristics — screen size, fonts, GPU, timezone, and more. The Electronic Frontier Foundation found that only about 1 in 286,000 browsers share the same fingerprint, so most people can be recognised across sites without any cookies at all.

Can a website see my exact location?

By default a site only sees your approximate city, derived from your IP address. Pinpoint GPS location — accurate to a few metres — requires your explicit permission, but many apps and sites request it as a matter of routine.

Can websites see my other tabs or which sites I'm logged into?

No. The browser sandbox and same-origin policy stop any page from reading your other tabs, your history, or another site's data. However, a page can still detect the moment you switch away from its tab, the site you arrived from, and — sometimes — which major services still recognise your browser session.

How do I stop websites from tracking me?

Install a content blocker such as uBlock Origin, use a privacy-focused browser (Brave, Firefox, or Tor), deny camera, microphone, location, and clipboard access by default, block third-party cookies, and turn on Global Privacy Control. Together these steps cut off the large majority of trackers.

Does this website store any of my data?

No. Every reading is computed inside your browser and never leaves it, apart from one optional lookup that turns your IP address into an approximate city. Visits are measured only with anonymous, cookieless counts that cannot identify you.

Can online stores really tell it's me on both my phone and laptop?

Often yes — not from your browser, but from your identity. When you log in or check out, your hashed email and phone are matched against your logged-in accounts on ad platforms, which you use on every device. That links all your devices to one profile, even without cookies.

Does an ad blocker stop e-commerce tracking?

It stops a lot of it — browser pixels and ad scripts — but not server-side tracking, where the store sends your purchase data to ad platforms from its own backend. To limit that, minimise the real data you give at checkout (guest checkout, email aliases) and turn off ad personalisation in your platform accounts.

How E-commerce Tracks You Across Sites, Devices, and Ads

Yes — e-commerce can recognise you across different sites, across your phone and laptop, and inside ad platforms like Meta and Google. It rarely relies on one trick; it layers several so that even if you block one, the others still connect the dots. Here's how the machine works.

Updated July 2, 2026 · 7 min read

Tracking pixels: the starting point

Most stores embed third-party 'pixels' — small snippets from advertising platforms such as the Meta Pixel, TikTok Pixel, and Google Ads tag. Every product you view, search, add to cart, or buy fires an event back to that platform, tagged with identifiers.

Because the same pixel sits on thousands of unrelated sites, the ad platform sees your behaviour across all of them, not just the one store. That shared presence is what makes cross-site tracking possible in the first place.

Server-side tracking that you can't block

As browsers block third-party cookies and ad blockers stop pixels, stores moved tracking to their servers. Tools like Meta's Conversions API and server-side Google Tag Manager send your purchase and browsing events from the store's backend directly to the ad platform.

This bypasses your browser entirely, so a content blocker can't see or stop it. The store matches the event to you using data you handed over at checkout — email, phone, name, address.

How they link you across devices

The glue for cross-device tracking is usually your identity, not your browser. When you log in, subscribe, or check out, the store collects your email and phone number. These are hashed and sent to ad platforms, which match them against the hashed email or phone on your logged-in Meta, Google, or TikTok account.

Because you're logged into those platforms on every device, the match links your laptop, phone, and tablet to one profile. This is called identity resolution, and 'identity graphs' from data brokers extend it further by merging records across companies.

Hashed email/phone matching ties an anonymous visit to your real account.
Logged-in ad-platform accounts connect all your devices to one identity.
Mobile advertising IDs link in-app behaviour to web behaviour.
Data-broker identity graphs merge profiles across unrelated businesses.

What they do with it: retargeting and personalisation

Retargeting ads: the shoes you viewed follow you across other sites and social feeds because the pixel reported the view.
Abandoned-cart emails and ads: leaving without buying triggers reminders, sometimes within minutes.
Lookalike audiences: your profile is used to find and target strangers who resemble you.
Price and offer personalisation: some sites vary prices, discounts, or shipping offers based on your device, location, and history.
Email and SMS remarketing: your address feeds ongoing campaigns, often shared with partners.

How to break the chain

Install uBlock Origin to block pixels and ad scripts at the source.
Use guest checkout and a dedicated email alias per store to make identity matching harder.
Log out of Meta, Google, and TikTok while shopping, or use a separate browser profile for them.
Turn off ad personalisation in your Google, Meta, and TikTok account settings, and reset or limit your mobile advertising ID.
Block third-party cookies and enable Global Privacy Control to send a legal opt-out where it applies.

Frequently asked questions

Can online stores really tell it's me on both my phone and laptop?: Often yes — not from your browser, but from your identity. When you log in or check out, your hashed email and phone are matched against your logged-in accounts on ad platforms, which you use on every device. That links all your devices to one profile, even without cookies.
Does an ad blocker stop e-commerce tracking?: It stops a lot of it — browser pixels and ad scripts — but not server-side tracking, where the store sends your purchase data to ad platforms from its own backend. To limit that, minimise the real data you give at checkout (guest checkout, email aliases) and turn off ad personalisation in your platform accounts.