Open the model on 0xr.space, press Scale in the dock (it shows the current percentage), then Measure. Tap one point on the model, then a second: a line joins them and its length appears, like ~ 42 cm. A third tap starts a new measurement. It works with a mouse or a finger in a browser, on an Android phone in AR, and with a pinch in VR on Meta Quest.
The points land on the bounding box of the part you tap, not on its exact surface, which is why every reading has a ~; on a model of one part, that box is the whole model's. The length follows the scale on show, so measure at 1:1 Size to read real dimensions. Lengths are in centimetres and metres only. It is not a survey or CAD measuring tool.
The points are taken on the tapped part's bounding box, not its surface, so the number is an estimate.
No. Lengths are shown in centimetres and metres only.
The model as it stands. At 50% scale a 1 m edge reads about 50 cm, so press 1:1 Size first, and check the file's units are right.
No. It is read on the device, and nothing is sent to a server unless you create a share link yourself.