When you sign up for iCloud, you automatically get 5GB of free storage for your iOS backups, photos, videos, documents, and apps. When you turn on iCloud Photo Library, the Photos app lets you know if you need more space to upload your library.
Reduce the size of your Photos library
You can reduce the size of your Photos library by exporting photos and videos you don't want or need.
- Select the items in Photos. Choose File > Export, and follow the instructions.
- Delete the exported items. Then choose File > Show Recently Deleted and click Delete All to permanently delete the items from your library.
Start a new photo library
You can create a new Photos library to use with iCloud Photo Library. Remember to designate this library as the System Photo Library.
- Hold down the Option key while opening Photos.
- Choose Create New.
- Import content from your previous library to create a new, smaller library.
Split your library with Aperture
If you use Aperture, you can split your iPhoto or Aperture library to create a smaller library to use with iCloud Photo Library.
- Open your photo library in Aperture.
- Select the content you'd like to export as a new library.
- Choose File > Export > Items as New Library.
After the export is complete, you can migrate this new Aperture library to Photos and turn on iCloud Photo Library.