Pryglass (formerly Signal/Block) is a Safari extension that shows what a web page actually does while you use it: what it stores on your device, which other companies it talks to, whether it runs fingerprinting code, and when it reaches for things like your location, camera, microphone or clipboard. Everything is worked out on your device. Nothing you browse is sent to the developer or anyone else.
What it shows
- Storage and cookies. Which cookies, local storage, IndexedDB and other stores a page reads or writes (names only, never the stored values).
- Network calls and third parties. Which servers the page contacts, which of them belong to other companies, and what those third parties are for (analytics, advertising, session recording, content and more).
- Fingerprinting. Canvas, WebGL, audio and font checks that can be used to recognize your device without cookies.
- Sensitive features. Requests for location, camera and microphone, clipboard reads, WebRTC connections, notifications and permission checks.
- Form activity. When you focus or type in a form field, what kind of field it is (password, payment, account or search). Pryglass never reads what you type.
- A trust score for each page (0 to 100: Few, Some or Many concerns) with the main factors behind it, and each event marked Routine, Noteworthy or High sensitivity.
- What changed since your last visit, compared with that page's own history on your device, and an optional Unusual visit check that spots visits that differ from your earlier ones.
- Top trackers on the current page (analytics, advertising and session recording), with how many of the sites you inspected in the last 30 days each one also appeared on, and watched sites: changes on a watched site are highlighted when you open Pryglass there.
- Blocking. Block a third party on this site or on all sites. Safari applies the rules you choose. Nothing is blocked until you choose to block it.
For everyday browsing
Open Pryglass on any page and the answer comes first: a trust score with the main factors behind it. Underneath, in plain language: who the page talks to, what it keeps on your device, and anything unusual. Block the trackers you don't want, on that site or on all sites.
Safari's Privacy Report tells you how many known trackers Safari kept from profiling you. Pryglass shows what each page actually did. It works alongside your ad blocker rather than replacing it.
For web developers and privacy professionals
See the API calls behind the summary: request type, method and address, storage operations by store and key, fingerprinting evidence, the frame and script location that triggered each call, and how often it repeated.
Use Copy summary for a readable Markdown report of the current page, or Copy data (JSON) for the raw events. Use it to check your own site's third parties and storage use in real Safari on iPhone, iPad and Mac.
How it works, on your device
When a page loads, Pryglass's content scripts watch the browser features the page uses and the resources it loads, inside Safari on your device. The extension collects the findings, classifies them with rules built into the app, and shows them when you open it. There is no Pryglass server: the extension makes no network requests of its own, has no analytics or crash-reporting code, and needs no account.
When you open Pryglass on a page, it saves a short summary of that visit on your device so it can tell you what changed next time: the site name and page path, counts, the domains of third-party companies, and the trust score. It never saves query strings, request addresses or anything you typed. Saved history is capped, removed after 90 days, and you can delete it at any time with Delete saved history. Private Browsing tabs are analyzed live, but nothing from them is saved. This describes version 1.2 and later; the privacy policy has the details, including how earlier versions differ.
Detection is based on heuristics. A flagged item is a reason to look closer, not proof that a site is doing something wrong, and some tracking can go unseen.
Set it up
After installing, turn the extension on in Safari and allow it on all websites. It takes about a minute, and you only do it once. Without website access, Safari doesn't let Pryglass see the pages you visit.
The Pryglass app walks you through the same steps. On a Mac, and on iPhone and iPad with iOS or iPadOS 26.2 or later, it also shows whether Pryglass is turned on in Safari and has a button that opens the settings for you (Open Safari Settings on Mac, Open Settings on iPhone and iPad).
iPhone and iPad
- Open the Settings app and go to Apps > Safari > Extensions > Pryglass.
- Turn on Allow Extension.
- On the same screen, under Permissions, set All Websites (it may say Other Websites) to Allow.
- Optional: to include private tabs, turn on Allow in Private Browsing. Nothing from private tabs is saved.
Then open a website in Safari, tap the page menu button in the address bar, and tap Pryglass. If Safari asks, choose Always Allow on Every Website. Reload pages that were already open.
Mac
- In Safari, choose Safari > Settings, then click Extensions.
- Select the checkbox for Pryglass.
- With Pryglass selected, click Edit Websites… and set When visiting other websites to Allow. Or click the Pryglass toolbar button on any page and, if Safari asks, choose Always Allow on Every Website.
Then open a website and click the Pryglass button in Safari's toolbar. Don't see it? Choose View > Customize Toolbar… and drag Pryglass into the toolbar. Reload pages that were already open.
Using it
- The trust score and its main factors sit at the top. See details opens Insights.
- Activity lists the events Pryglass saw on the page. Tap or click one for details. The ⓘ button (Explain) gives a plain explanation: what was seen, why it matters, how sure Pryglass is and what you can do.
- In Insights, see the third parties on the page and block the ones you don't want, on this site or on all sites.
- Watch site marks a site you care about. Next time you open Pryglass there, it highlights what changed.
- More (top right) holds your blocked domains, watched sites, options, Delete saved history, and links to help and this site.
Get Pryglass
One purchase from the App Store covers iPhone, iPad and Mac. No subscription, no account, nothing to buy inside the app. Requires Safari 18.4 or later: iOS or iPadOS 18.4 or later, or macOS Ventura (13) or later with Safari 18.4 or later. View Pryglass on the App Store.
Questions or problems? See Support. For what happens to your data, read the privacy policy.