Browsers & Accounts · Extensions: Helpful or Harmful · Lesson 1 of 5

What Extensions Can See

Read extension permissions in plain words and limit where each one works.

Permissions in Plain Words

An extension is a small add-on program that lives inside your web browser. It adds a feature, like blocking ads, finding coupons or editing PDFs. Chrome, Edge, Firefox and Safari all support them.

To do its job, an extension asks for permissions. A permission is a kind of access the browser lets the extension have. The browser shows these when you install it, and you can see them again later.

Here is what common warnings really mean:

• Read and change all your data on all websites means the extension can see everything on every page you open. That includes emails, bank balances and what you type into forms. It can also change what the page shows you.
• Read and change your data on a number of websites means the same power, but only on the sites it lists.
• Manage your downloads means it can see, start and open files you download.
• Read your browsing history means it can see every site you visit.

In Firefox, the all sites warning says Access your data for all websites. It means the same thing.

Some extensions truly need wide access. An ad blocker has to look at every page to remove the ads. That is why it matters who made it and how much you trust them.

The question to ask is simple. Does this power match the job? A coupon finder that wants your downloads and every page is asking for far more than it needs.

To see the list in Chrome or Edge, open the menu, choose Extensions, then Manage extensions, then Details under one extension. In Firefox, open Add-ons and themes and choose the extension. In Safari on a Mac, open Safari, then Settings, then Extensions.

On the practice computer, open the extensions page and review each extension's permissions. Remove the coupon extension added yesterday and the one added by a program on your computer. Keep the ad blocker.

Choosing Where an Extension Works

You don't always have to give an extension every site. Most browsers let you choose where it is allowed to run. This choice is called site access.

In Chrome and Edge, open Manage extensions, pick an extension, and choose Details. Under Allow site access (Chrome) or Site access (Edge) you will see three choices:

• On click (Chrome calls it On select). The extension does nothing until you click its button. Then it works only on that one tab, and only until you close it.
• On specific sites. It runs only on sites you add to its list, such as one shopping site.
• On all sites. It runs everywhere, all the time.

You can also click the puzzle piece icon in the toolbar. It is the Extensions button, and it shows which extensions can read the page you are on.

In Safari on a Mac, click the extension's button in the toolbar or open Settings, then Extensions. You can choose how much access it has on each website. In Firefox, some extensions let you turn site access on or off in the extension's Permissions tab.

A good rule is to start small. Give an extension the least access that still lets it do its job. A tool you use once a week, like a screenshot helper or a translator, works fine on click. A tool for one site, like a price tracker for one store, belongs on specific sites.

On all sites is for the few tools that truly need it, like a trusted ad blocker or a password manager from a company you know.

If an extension stops working after you limit it, nothing is broken. Just click its button when you need it.