User clicks the extension icon → protractor overlay appears centered on the current page → user drags two guide arms to align with a vertex → angle is displayed in real-time → user can resize, rotate, lock, nudge, and customize appearance via options page → click extension icon again to hide

Target users: Students and educators measuring angles for geometry/math / Designers verifying angles in web layouts or images / Engineers and architects inspecting visual diagrams / Government agencies and schools (mentioned in FAQ)

Monetization

No paid features detected

Extension is fully free and open source under MIT license. No premium/upgrade/billing/subscription/plan keywords found anywhere. The 'subscribe' hits are from the PubSub (publish-subscribe) messaging pattern used internally, not payment subscriptions. The only monetization is a voluntary 'Buy Me a Coffee' donation link on welcome.html. No features are gated behind payment.

Confidence: 100
Payment platform: --
Source: AI / High
Login required: No
Reason: The extension is a purely local overlay tool. It uses chrome.storage.sync for saving user preferences and chrome.scripting to inject CSS/JS into the active tab. There is no authentication flow, no account creation, no API keys, and no destination service requiring login. The 'account' hit in guide.js:132 is a code comment about math: 'Must account for global rotation'

Permission risk

Medium-risk permissions

This estimate uses declared permissions and host permissions to assess access scope and sensitivity.

扩展能力较强：activeTab、storage、scripting

Publisher

ben.burlingham

Independent publisher

Email: [email protected]
Phone: --
Address: --

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Permissions

Host access