When to start registry?

We used Amazon and started ours right away. We didn't link it to our website until we were finished but it was nice to start it and add things as we thought of them, and if we added silly things it gave us time to realize we didn't need them and take them off (like a juicer we would never use but impulse added haha).

I would wait. We just did our registry in February (bridal shower is in May and wedding is in August) and I already have 6 items that have gone out of stock or been discontinued. I would probably do it 2 months before your shower and then you may need to refresh it a bit for the wedding.

We started ours right away too but didn’t link it to our website til a while

We did ours about 10 months out because a lot of guests bought us gifts early to celebrate our engagement and they asked for our registries. But a lot of things did get discontinued or go out of stock and it was something I had to constantly monitor and update.

We started ours almost exactly a year out. We put in an offer on a house and got excited.
We've definitely had to go back and change things.
If you're planning on having a wedding website, and listing it on a save the date, I'd suggest doing a registry at least a month before those go out. It's annoying to change things on the registry when they get discontinued, but we weren't feeling pressure to register. And we've gone on a date night or two to update it too.

We started our Amazon registry pretty soon after getting engaged. I wanted to at least have some stuff on there so we could link it on our wedding website for when our save the dates went out.

We started building ours right away but didn't make it public until shower invitations went out