Use a “keep or delete” session inside Photos on your iPhone.
- Open Photos, tap Library, then All Photos.
- Scroll to the oldest year.
- For each day, tap Select, then quickly mark obvious trash: receipts, screenshots, duplicates, blurred pics.
- Aim for one month per day so it feels light.
- When done, go to Albums, Recently Deleted, and empty it to free iCloud space.
Most people have photos as their biggest iCloud use. Clearing 1,000 photos often frees around 2 to 3 GB.