Put them on and look at a bright light. You shouldn't be able to see anything. It's not foolproof, but cheap fake glasses are usually so bad that you can see household lights through them.

You can also see if the brand you have is on this list, although someone could have faked a reputable brand name: https://eclipse.aas.org/resources/solar-filters

There is a False Reject/Accept problem here.

If you believe your Amazon email, all glasses are fake (at least I've got email saying so for glasses I know are good).

If you want a quick way to weed out bad glasses, see if you can see a compact fluorescent light bulb, with the glasses... if you can, they are bad. Unfortunately, you could still have bad glasses that happen to just block fluorescents.

I used a spectrometer and a calibrated light source, but that seems like overkill for most folks.

One trick I recommend is putting the reflective foil inside some regular sun glasses. It's uch more comfortable, and you get some extra IR/UV protection.

Most of them aren't actually 'fake', they are just not rated high enough to look directly at the sun. I bought a ten pack on ebay on Friday, and only 2 pairs were ISO 13 or higher, the other 8 pairs were ISO 5 grade. They are still ISO rated, just not for eclipses. So to check, look and see what rating you have on your glasses and look for >13.

I have the same question. I ordered some from Amazon for my kids. I hope this article means that they were carefully verified by Amazon, but it has still made me uneasy about using them. Just knowing fakes are common is really concerning.

Afterwards, you look around and ask yourself: "Do I truly see?"