Most guidance about buying VR tells you what to look for on the product page. This page is about the other half: once the file is on your drive or playing in your headset, how do you find out what you actually received? Every check below can be done by anyone, on any clip, without special software.
The frame is the first answer
A VR180 file is wider than it is tall by a factor of two — 3840×1920, 5760×2880, 7680×3840. That is not a stylistic choice, it is what side-by-side means: two square-ish eye images sitting next to each other in one frame. If your file is 1920×1080, or taller than it is wide, no amount of labelling makes it VR. A portrait phone clip filed under a VR category is still a portrait phone clip, and a headset will hang it in front of you as a small floating rectangle.
You do not need a tool for this. Any file manager will show the dimensions in the file’s properties, and every player shows them somewhere in a media-info panel. It takes ten seconds and it settles the largest question.
Two eyes or one
The second check is whether the two halves of that wide frame are actually different. Pause the clip, look at the left half and the right half, and compare something close to the camera against something far away. In a genuine stereo recording the near object sits at a visibly different position in each half; that offset is the depth. If the halves are identical, the file was duplicated rather than shot with two lenses, and it will look like a flat picture pasted onto a curved wall — large, but with no sense of distance.
This one matters more than it sounds. Duplicating a single image into a side-by-side frame is trivial, produces a file with all the right dimensions, and passes every automated check that only looks at the container.
Resolution is per eye, not per file
Headline numbers usually describe the whole frame, so an “8K” VR180 file is 7680 pixels wide across both eyes and therefore roughly 4K to each of your eyes — spread across a field of view far wider than a television. This is why VR needs numbers that sound absurd next to flat video, and why a “4K VR” clip can look softer in a headset than a 1080p clip looks on a monitor. Halve the headline figure before you compare anything.
What the player is actually receiving
Streaming players choose a quality rung on the fly. Most of them will tell you which one, usually in a statistics or debug overlay, and it is worth looking during playback rather than trusting the number on the shop page. Watch it for a minute: if it climbs to the top rung and stays there, the file is what was advertised and any earlier softness was your connection warming up. If it never climbs on a connection you know is fast, the higher rungs are not being served.
The distinction is worth making before you complain, because the two cases get different answers. A shop can fix the second one. Neither shop nor producer can do anything about the first.
Download versus stream, at this file size
These files are large — several gigabytes for twenty minutes is ordinary, not a mistake. A download plays at full quality every time and costs you the storage. A stream costs nothing to keep and puts the quality at the mercy of the connection each time you watch. Which of the two a shop offers is worth knowing before you buy, and it is the single thing most likely to explain a disappointing first viewing.
If it turns out to be flat
Ask the seller. A clip sold as VR that has one eye image, or a frame that is not twice as wide as it is tall, is not a matter of taste and most producers would rather know. Keep the measurement you took — the dimensions and, if you have it, a paused frame showing both halves are identical. That is a concrete claim rather than an impression, and it is much harder to wave away.
This site cannot help with any of that. It lists clips and links to shops; the purchase, the refund and the conversation all belong to the producer.