Depending on the software version in which you create a shared album, there are limits to the number of photos, albums, and invites you can share.
If you reach your shared album limit, you need to delete some photos or videos before adding new ones. The photos and videos you share (and the comments or likes associated with those photos) stay in iCloud until you or the contributor delete them manually, or until you delete the shared album completely.
Photos and videos in shared albums you own are stored in iCloud in their original formats at full resolution, and they count towards your iCloud storage. The photos and videos participants add to your shared album also count towards your iCloud storage.
There are no limits to the number of albums, or photos and videos in a shared album, beyond the owner's available iCloud storage.
Temporary shared albums don't count towards your iCloud Storage.
Maximum number of participants in a shared album, including the owner: 100
Maximum combined number of photos and videos from all contributors in any one temporary shared album: 5000 (the file size of each item is not limited)
Photos and videos in your shared albums are kept in iCloud, but they don't count towards your iCloud Storage.
These are the shared albums hourly and daily limits:
Maximum number of photos and videos from a single contributor across all shared albums, per hour: 1000
Maximum number of photos and videos from a single contributor across all shared albums, per day: 10,000
Some additional limits for shared albums:
Maximum shared albums an owner can share: 200
Maximum shared albums a user can subscribe to: 200
Maximum subscribers per shared album: 100 (the number of subscribers on each shared album)
Maximum combined number of photos and videos from all contributors in any one shared album: 5000
Maximum number of comments per photo or video in a shared album: 200 (a comment can be either a like or a text entry)
Maximum characters per comment: 1024
Maximum number of invites a shared album owner may send per day: 200
When shared, photos are reduced to 2,048 pixels on the long edge, except panoramic photos, which can be up to 5,400 pixels wide. You can share GIFs that are 100 MB or smaller.
Videos can be up to fifteen minutes in length and are delivered at up to 720p resolution.
Sharing Suggestions are limited to 5000 items with a maximum share size of 1GB.
Not all features are available in all countries or regions.