A photo library fills a PC predictably, and it is fixable by workflow

Photography fills a PC in a predictable order: originals, then previews, then exports, then the copies that exist because two applications each wanted their own. Only the first is irreplaceable.

Where it goes

The setup

1. Originals on a large drive, organised by date, with a second copy elsewhere.
2. Catalog on the system SSD, because it is small and constantly written to.
3. Previews sized to your screen rather than 1:1 for everything, discarded after 30 days.
4. Exports treated as disposable, removed after delivery.
5. One library, not two.

The Windows specific trap

The Pictures folder is a known folder that several things write to by default: the camera import wizard, OneDrive, the Photos app and any phone sync tool. A machine can end up with the same photos in three places without anyone choosing that, which is why OneDrive's local copies matter here more than anywhere else.

Get-ChildItem "$env:USERPROFILE\Pictures" -Directory -Force -EA SilentlyContinue |
  ForEach-Object {
    $s = (Get-ChildItem $_.FullName -Recurse -Force -File -EA SilentlyContinue | Measure-Object Length -Sum).Sum
    [PSCustomObject]@{ GB = [math]::Round($s/1GB,2); Folder = $_.Name }
  } | Sort-Object GB -Descending

Previews are the largest reclaim

1:1 previews are full resolution renders built per photo, and on a large catalog they exceed the originals. Setting the catalog to discard them after a week or a month is the difference between a folder that stabilises and one that only grows, covered in photo editors on Windows.

Culling is the only real answer to originals

Previews rebuild and exports re-export, so the only category that grows without limit is originals. A culling pass at import, deleting the obvious failures before they are ever backed up, compounds over years in a way no cleanup does.