I have a few apps on my phone for which the only purpose is to open and bring up a barcode (ex. Tim Hortons Scan and Pay). I'd love to delete the app and only have an Apple Wallet thing.
So far as I can tell this still requires an pass/wallet signing certificate from the apple developer program to use, so you can't use it to create ad hoc passes, unless you already have a $100 developer subscription.
I use an app called pass2 u wallet for this, it's clunky but works well. No affiliation.
Look for the SuperCards app. I have that for my pc optimum, metro, Canadian tire cards / barcodes. No more carrying 1000 loyalty cards around.
As of iOS 27 you can do this yourself, or physical barcodes, they just don’t look as nice as what this program can do.
Starbucks on Google can be added to Google Wallet. But then I went to use it and they told me to close wallet and open the app. Shrug.
I've had patchy success with adding boarding passes to the wallet too. Support seems half baked.
iOS 27 includes this feature built in now
Anycode Wallet! I used it years ago to put my family’s library card in Apple Wallet. It supports a bunch of standards, and also you can use a photo (which I ended up using because my library uses some weird non-standard bar code).
Edit: also, it’s free.