How do I detect browser extensions? View extension IDs and fingerprinting results online

Open your browser's extension manager and you'll often find a dozen or more add-ons sitting there — a translator, an ad blocker, a password manager, a screenshot tool. Most of the time they stay quietly out of sight, but some of them leave recognizable traces on the pages you visit.

A browser extension detection tool shows you which extension details your current setup exposes. Keep in mind that the results are not a complete inventory of what's installed. What a website can actually identify depends on how an extension runs, how it exposes its resources, and the rules the detection tool uses.

1. Browser extension detection: what can it actually find?

A regular website can't read the full list of extensions installed in your browser. It has to infer things from resource access and page-level clues. What's typically detectable:

•  Extension ID: Some Chrome extensions have stable IDs that can be identified indirectly through known resource signatures.

•  Extension name: Matched against an existing signature database using the detected ID.

•  Extension version: Certain versions have distinctive resources or behavior, though the match isn't always reliable.

•  Script injection traces: Some extensions modify the DOM — adding nodes, styles, or specific attributes.

•  Resource loading: Checks whether specific extension resources are reachable from the page.

Keep in mind that Chrome restricts how extension resources can be accessed. Under Manifest V3 in particular, an extension has to explicitly declare which resources web pages are allowed to reach — knowing an extension's ID doesn't give you access to any file you like.

That's why the extension details shown on a detection page are best treated as fingerprint signals rather than a full record of installed software.

2. Check your browser's extension signals online

Want to see which extension signals your browser is giving off? Run an online check with ToDetect.

Open the ToDetect browser extension detection page, wait for the scan to finish, then review the detected extensions and the related fingerprint details.

A few things worth paying attention to:

•  Whether your current setup exposes any recognizable extension signals.

•  Whether the extension details shown match what you actually have installed.

•  Whether the results change from one scan to the next.

Next, type chrome://extensions into Chrome's address bar and turn on Developer mode. That shows you the ID, name, and version of every extension installed on your machine.

Comparing the local list with the online results gives you a first sense of which extensions may be leaking signals to web pages. The two won't always line up, and that alone doesn't mean something's wrong — they collect information in completely different ways.

3. Why do installed extensions sometimes not show up?

This comes up a lot in extension detection. Say you have a translation extension installed, yet the scan doesn't return its ID. It may not expose any accessible resources to the page you're on, or it may only run on certain sites.

Detection tools also lean on an existing signature database. If an extension hasn't been catalogued yet, or an update changed its resource paths, the match can fail.

Some extensions barely touch the DOM at all, leaving outside sites very little to observe in the first place.

So a missing result doesn't prove an extension isn't installed, and it doesn't mean no page anywhere will ever see a trace of it. Likewise, if an ID does turn up, check it against your local install list — don't treat a probable match as a confirmed finding.

4. Why do extensions affect your fingerprint?

A browser fingerprint is usually assembled from signals like User-Agent, language, time zone, screen resolution, Canvas output, and fonts. Some extensions also produce behavior that pages can observe, which shifts the fingerprint you present.

Not every extension exposes identifiable signals, though, and the number you have installed doesn't directly make your fingerprint more unique. What matters is how an extension runs, what resource access it's granted, and how much a website can actually observe.

5. Extension security checks: don't skip permissions

Beyond fingerprints, it's worth reviewing extension permissions on a regular basis. On any Chrome extension's details page, you can see the site access and other permissions it has requested.

For example, storage is mainly used to save an extension's own data; tabs may let it read information about your open tabs; cookies, combined with the right site permissions, allows it to read or manage cookies for those sites; and debugger grants powerful debugging control.

The key question is whether the permissions match what the extension actually does. If a simple web utility is asking for access to large amounts of unrelated site data, that deserves a closer look.

Also check the developer, where you installed it from, when it was last updated, and what users are saying. For anything you no longer use or can't trace back to a trusted source, it's worth reconsidering whether to keep it.

FAQ

Can a website see every extension I have installed?

Usually not. Regular web pages have no API for enumerating installed extensions. They can only make limited inferences from observable resources and page characteristics.

Why do two scans in the same browser return different results?

It can come down to whether an extension is enabled, its site access settings, a browser update, or adjustments to the detection rules. Some extensions only run when certain conditions are met.

Do extensions show up in Incognito mode?

Chrome extensions are blocked from Incognito by default, though you can allow them individually. Whether detectable signals appear still depends on whether the extension is running and what it actually does.

What should I do if I see an extension ID I don't recognize?

Start by checking chrome://extensions. If nothing local matches, look into how the result was matched before drawing conclusions — don't assume something's wrong based on an ID alone.

Final thoughts

The real value of extension detection isn't a list of what you've installed — it's understanding which extension signals a website can actually observe.

Run a scan on ToDetect to see which extensions it can identify, then cross-check IDs, versions, and permissions in Chrome's own extension manager. Together, the two give you a clearer picture of your current browser environment.

It's worth running the check again after you install something new, change permissions, or update your browser, and keeping a record of what you find. Knowing what your extensions do and what they're allowed to reach will help your day-to-day privacy far more than counting how many you have.