What - if anything - is my Global Entry card good for?

You don’t need the card at immigration BUT it is a valid ”REAL ID” so you can use it to board a plane.
https://www.tsa.gov/sites/default/files/resources/realid_factsheet.pdf

Thank you, Laura!

We have received Global Entry cards both when we first signed up and when we renewed our Global Entry. I have never had to show them.

One time a few years ago we flew back into the US via Chicago, I think. The Global Entry kiosk were down and the regular line was super long. However CBP agents were announcing that if you had your GE card you could skip to the front of the line. I did not have my card, but have vowed to never travel again without it.

It would suffice for land or sea border crossings in North America, in lieu of a passport or passport card.

Oh, CJ that's really good to know. Thank you all for helping to clarify how this card can be useful!

If you are flying out of a Canadian airport, having the Global Entry card also permits you entry to the Trusted Travellers security screening line, which has streamlined security screening, i.e. you can keep your shoes/belt/jacket on and liquids/gels in bag (though you must remove laptops regardless).

(Note that if you are heading to the US from a Canadian airport with preclearance, you can still use the Global Entry kiosks at US preclearance without the card, just as is the case at any port of entry in the US. This is separate from the security screening lines, though if you are flying from Canada to the US you are likely to do one step right after the other.)

If you ever fly through St Thomas - they require you show the card to get through the GE line. It's the only place I have ever had to show my card

I carry my card for reasons mentioned above: It's a form of official ID and if for some reason the GE kiosks are not working, it shows I have GE and I will be given special treatment.

By the way, my record for stepping off the plane, through immigration, and stepping outside the terminal is 8 minutes thanks to GE. It was at Terminal 7 JFK.

I have Global Entry and use it as my ID when traveling in the US. If you input the GE # when you make your domestic reservations, you automatically get TSA Precheck. In some airports, in my experience specifically, you have to scan your GE card when going through Precheck. This was the last 2 times I visited my daughters in May and last week.

We've never been asked to show the cards, or seen where it could be scanned. All the info on your GE status comes up with your passport scan. If humans ask if you have a card, its probably because they don't want non-GE folks sneaking into the wrong (shorter) line. The number is what matters for pre-check.

I thought the main reason for it is to shorten the immigration lines when traveling back to the USA.

You do not need to show your GE card when going through pre-check but you can use it. You are asked for ID. The last few times I flew I didn't even need my boarding pass. I inserted my drivers license into the machine, the TSA agent looked at the screen, asked me to lower my mask to make sure it was me, and off I went. My driver's license number is tied to my Trusted Traveler number. (There is no such thing as a GE number.)

By the way, just because you have a trusted traveler number from GE doesn't mean you automatically get Pre-Check. Occassionally, you might be denied as a random check.

I keep my GE card, as well as my Passport card, in my money belt just in case I need it.

CaliMom--GE helps to shorten the regular immigration line. We are talking about the card we get that isn't necessary in most cases to use when going through Global Entry.

Frank, What is a passport card?

Susan, when you apply for a passport (nowadays) there is an extra-cost option to get a Passport Card, which can be used as a photo ID and for those land-border crossings. Not a substitute for a passport itself.

So much useful information! Thanks to everyone who has posted. Clearly I'll be taking my GE card with me whenever flying - even domestically - or traveling out of the country. As my state driver's license is not yet Enhanced, the GE card will be easier to carry than will my passport, when the requirement for an Enhanced ID (is that the right term?) for flying kicks in sometime in - 2023? Thanks again!

when the requirement for an Enhanced ID (is that the right term?)

No that’s something else, more like a global entry card issued by a state DMV. The term you are looking for is Real ID compliant state driver license or state ID card. BTW that type of license had been offered for some time in LA, if there’s a gold star in the license upper right corner then you have it.

Thanks Tom. You're right that it's a Real ID. Yes, I misstated the kind of ID that we will need at TSA in the future. I can't keep up and my dear state of Louisiana is lagging behind... at least in the ID department. They now (finally!) offer it with license renewals, but mine's not due to be renewed for a few more years, so I'll plan to carry my Global Entry ID when Real IDs become mandatory at TSA.

Why not contact the Louisiana DMV, or whatever they call it, and find out if they will reissue your DL for Real ID?