Online Protractor

Drag the vertex and ray handles, optionally place them over an uploaded image, inspect the smaller/reflex angle and use snapping without uploading the image.

Angle display

Snap while dragging

Precision

Optional background image

The image stays in this browser. Align the vertex and two ray handles to the angle you want to inspect.

Measured angle—

Angle type—

Reflex angle—

Supplement—

Drag the three blue handlesCenter = vertex. The two outer handles define the rays.

Interpretation: screen/photo alignment is a visual estimate. Perspective distortion, lens distortion and imprecise handle placement can change the result; use proper measuring equipment for critical work.

Device diagnostic workflow

Start with a functional check, measure only what the browser can actually expose, then retest after one change.

ConnectChoose the actual browser-visible device or grant permission when required.

TestConfirm basic signal, input, output, preview or display behavior.

MeasureUse browser-exposed levels, timing, resolution, FPS, axes or event data.

DiagnoseCompare the symptom with the focused diagnostic rather than guessing from one number.

RetestRepeat after changing the device, cable, permission, browser or system setting.

Pre-call Mic Webcam Keyboard Mouse Gamepad Display Permissions

Browser boundary
These tools observe browser APIs and local media/event streams. They cannot certify hardware condition, bypass denied permissions, or expose measurements the browser/OS does not provide.

Use the connected diagnostic workflow

Connect or select the device, confirm the basic function, inspect the browser-visible measurement, then open a focused diagnostic only when the symptom calls for it.

Browser-local does not mean laboratory measurement

These pages can report Web API data such as events, stream settings, frame timing and audio samples. They do not certify hardware condition or bypass browser and operating-system limits.