What the sizes mean

When you finish, you can read any number in PoppyDisk without guessing what it counts.

Size on Disk, and Size

Every number in PoppyDisk is Size on Disk: the bytes an item actually occupies on its Drive. The Disk Map, the Details Panel, the Tree view, the Cleanup Basket, and the Recovered Space report all use it, because it is the only measure that tells you what deleting the item would give back.

Size is how many bytes the item holds, the figure File Explorer's Size column shows. It appears in the Inspector beside Size on Disk. The two differ for compressed files, sparse files, and Cloud-only files, where the bytes on the Drive are far fewer than the bytes the file holds. Trusting Size for those would promise space that deleting them cannot return.

Unknown Space

A Drive's used space is what Windows reports for the whole Drive. A Scan measures the folders. The difference is Unknown Space, shown once, at the root of the Scan, hatched on the map and with a dashed icon in the Details Panel. It holds filesystem metadata, shadow copies, and whatever sits inside Restricted areas. PoppyDisk never spreads it across folders or folds it into Smaller Items, because it has no way to know where those bytes belong.

Restricted

A Restricted item is one the Scan could not read, because Windows keeps it private from a program running without administrator rights. It is purple on the map and says Size unknown where its size would be. It is counted as zero, so it never inflates a folder; the space inside it is part of Unknown Space instead.

To turn Restricted into measured space, see Measure Restricted areas.

Smaller Items

To keep the map readable, items under half a percent of their parent, and any beyond the sixty-four Segments a ring can hold, are gathered into one translucent Segment and one Details Panel row named Smaller Items, with the count of items inside it. Choose the row to expand it into concrete items, and search reaches inside it without expanding.

Smaller Items cannot be added to the Cleanup Basket as a group. PoppyDisk asks you to expand it and choose the actual items, so nothing is deleted that you never saw.

Hard Links

A Hard Link is one file reachable by several paths. The bytes exist once. PoppyDisk charges them to one of the paths, chosen the same way on every Scan, and shows the other paths at zero with a Hard Link badge. Every folder is then exactly the sum of its children, and no bytes are counted twice.

The consequence for cleanup: deleting a hard-linked path frees nothing while another path to the same content still exists. The Cleanup Basket warns you when an item is hard linked, and the Recovered Space report counts only what Windows confirmed. See Read your Recovered Space report.

Cloud-only

A Cloud-only file lives with its sync provider, such as OneDrive, and is not fully present on the Drive. PoppyDisk counts it at its Size on Disk, which is close to zero, and badges it in the map, the lists, and the Inspector. Deleting a Cloud-only file gives back almost no local space, and the Cleanup Basket says so before you do it. PoppyDisk never downloads a Cloud-only file, not even to preview it.

Links, junctions, and mount points

A symbolic link, a junction, or a mount point is shown as a leaf with a link badge and charged zero. The Scan does not follow it, so it cannot loop and cannot wander onto another Drive. To measure what sits behind a mount point, scan that Drive itself.

Approximate results

On ReFS, and wherever Windows deduplication or block cloning is in use, a file's bytes can be shared in ways no per-item measure can express. PoppyDisk marks such results approximate rather than presenting a precise figure it cannot stand behind.

Stale

A Stale size is one the Drive has changed since it was measured. PoppyDisk keeps the old number on screen so you can see what was there, marks the folder, and offers a Rescan of just that branch. See Refresh Stale results.