We are planning on keeping multiple versions of our docker images in the same repository as tags to keep them together. But is there a limit on how many tags we can keep or is it unlimited?
The answer is going to change over time. Right now, there is no programmatic limit on the number of tags you can have, but there is a practical limit.
Some docker operations and Hub UI operations try to query all the tags at once, and that query can time out if there are too many tags. I’ve seen this happen some times at around the 100 mark when there really are 100+ different images. If you have multiple tags on the same image then you can probably go higher.
So in the near term I would suggest removing your older tags to keep below 100 unique images.
Over time we’ll improve the behavior of the APIs so they don’t time out or they page their results better, or we may put programmatic limits in place (if we did something like this, we’d let people know ahead of time and help those with lots of tags migrate).