Are browser extensions safe? What to check before installing
Most extensions from official stores are safe, but it varies. Here is exactly what to check — permissions, developer, data handling — before you click Add.
Most browser extensions from the official Chrome Web Store and Firefox Add-ons are safe, but safety varies by extension — so it is worth a quick check before you install. The things that matter are the permissions it requests, who built it, what its reviews say, and whether it handles your data locally or ships it to a server. This guide walks through each check and the red flags that mean “don’t install.”
Extensions are powerful precisely because they can act on the pages you visit, and that power is also the risk. A safe extension asks only for what its features need and is transparent about what leaves your device; an unsafe one over-reaches or hides where your data goes. Knowing how to tell them apart takes about two minutes per install.
Are browser extensions safe to use?
Browser extensions are generally safe when they come from an official store, request only the permissions their features require, and are transparent about data handling. Risk rises with broad permissions, an unknown developer, or unclear data practices. The official stores review submissions, but review is not a guarantee — the final check is yours, and it is quick once you know what to look at.
What to check before you install
Before installing any extension, run five quick checks: the permissions it requests, the developer behind it, its reviews and rating, how it handles your data, and how recently it was updated. Each takes seconds, and together they catch the vast majority of problem extensions before they ever reach your browser.
| Check | What to look for | Warning sign |
|---|---|---|
| Permissions | Only what the features need | Access to sites it has no reason to touch |
| Developer | A named, reachable, reputable author | Anonymous or no contact details |
| Reviews | Steady ratings, no data complaints | Reports of odd behaviour or data grabs |
| Data handling | Clear on what leaves your device | Vague or missing privacy policy |
| Updates | Maintained recently | Abandoned for years |
Security teams converge on the same advice. Mozilla’s own guidance on assessing the safety of an extension stresses checking the developer, the reviews, and whether the permissions match the stated features — the same test you can apply in either browser’s store.
How to read extension permissions
Permissions are the single most important safety signal, because they define what an extension is technically able to do. Chrome and Firefox both show the requested permissions before you install, and Chrome’s developer documentation on declaring permissions explains that an extension must declare each capability it intends to use. If a request does not match a feature you can point to, treat it as a question, not a formality.
Broad host access
A permission to read and change data on “all websites” lets an extension see every page you open. Plenty of legitimate tools genuinely need it — anything that acts on any site does — but pair it with an unknown developer or vague data practices and it is a real risk. The key is whether the extension is transparent about what it does with that access.
Powerful capabilities
A few permissions warrant extra scrutiny: native messaging can run programs on your device, proxy settings can route your traffic through a third party, and debugger access can intercept encrypted traffic. These are legitimate for specific tools but rarely needed — if you cannot tie one to a feature, that is a reason to pass.
Red flags that mean don’t install
Some signals are strong enough to stop an install on their own. If you see these, the safest move is to choose a different extension rather than take the risk.
- Permissions that do not match anything in the description.
- No named developer, no contact details, no privacy policy.
- Reviews mentioning strange behaviour, pop-ups, or data concerns.
- A sudden new-permission request after an update, with no explanation.
- Not updated in years, or recently sold to an unnamed new owner.
How Manifest V3 changed the picture
Manifest V3 is the current Chrome extension platform, and it tightened the security model over the older Manifest V2. It limits how extensions run background code and pushes toward more constrained, auditable behaviour, which raises the baseline for what a new extension can quietly do. It is not a cure-all, but an extension built on the current platform is starting from a stronger position than a legacy one.
Keep extensions safe after you install
Vetting an extension once is not the end of it, because an extension can change after you install it. Safe use is an ongoing habit: review your installed extensions periodically, remove the ones you no longer use, and pay attention when an update asks for a permission it did not need before.
Prune what you do not use
Every installed extension adds to the surface an attacker could target, so the fewer you keep, the smaller that surface. Once or twice a year, open your browser’s extensions page and remove anything you have stopped using — dormant extensions still carry whatever permissions they were granted.
Watch for new permission requests
A trustworthy extension rarely expands its permissions without a clear, feature-driven reason. If an update suddenly asks to read data on all sites or to message your system, and you cannot connect it to a new feature, treat that as a prompt to re-vet — or remove — the extension rather than click through.
What a privacy-first extension looks like
The safest extensions minimise both permissions and data movement — they ask only for what their features need and keep your data on your device wherever possible. That is the standard worth holding any tool to, including ours: HotKeyNavigator runs your shortcuts, macros, and scripts locally, never transmits the page content, selected text, or keystrokes from the sites you use, and stores only your account email and plan on a server. Our privacy page spells out exactly what is and is not stored.
Local execution is a safety feature, not just a performance one: work that never leaves your machine cannot leak from a server it never reached. When you evaluate any extension — ours or anyone’s — apply the same checks in this guide, and favour tools that are specific and honest about what leaves your device.
Frequently asked questions
Are extensions from the Chrome Web Store automatically safe?
Not automatically. The store reviews submissions, which filters out much abuse, but review is not a guarantee and malicious or over-reaching extensions still slip through. Treat store presence as a baseline, then check the permissions, developer, reviews, and data handling yourself before installing.
What extension permissions should I be cautious about?
Watch for access to all websites, native messaging, proxy settings, and debugger access. Each is legitimate for specific tools but powerful enough to misuse. The test is whether the permission maps to a feature you can identify — if it does not match anything the extension does, be cautious.
How can I tell if an extension steals my data?
You cannot always tell for certain, but signals help: a missing or vague privacy policy, permissions broader than the features justify, reviews reporting odd behaviour, and an unknown developer. Extensions that run locally and clearly state what leaves your device are lower risk than those that are silent about it.
Does running an extension locally make it safer?
Yes, in a meaningful way. If an extension processes your data on-device and never transmits page content or keystrokes, there is no server copy of that data to breach or misuse. Local execution shrinks the attack surface, which is why privacy-focused tools emphasise it.
Is Manifest V3 safer than older extensions?
Manifest V3 tightened Chrome’s extension security model over Manifest V2, constraining how background code runs and making behaviour more auditable. It raises the baseline but does not remove the need to vet an extension. A current-platform extension starts stronger, yet you should still check its permissions and developer.
How many extensions is it safe to have installed?
There is no fixed number, but each extension adds attack surface, so keep only the ones you actively use. Periodically remove extensions you have stopped using, and be especially wary of any that request new permissions after an update without a clear reason.
Extensions are one of the browser’s best features and worth using — the goal is not fear, it is a two-minute habit. Check the permissions, the developer, and where your data goes, favour tools that keep work on your device, and you can install with confidence.