Explorer settings
Tip
TL;DR — Turn off Display file size information in folder tips. While it is on, resting the mouse pointer on a folder makes Explorer walk everything underneath it down to the last leaf, and on a mapped drive every level of that walk is a request to the server.
The tooltip that appears when you rest the pointer on a folder carries the folder's size. There is no such thing as a folder size to read: Explorer works it out by listing the folder, then every folder inside it, then every folder inside those, all the way down. On a local disk that is a few milliseconds of disk cache. On a mapped drive each of those listings is a round trip to the server.
Measured on one drive: pointing at a single folder — not opening it, only leaving the pointer on it — set off eighteen directory listings in about three seconds and reached seven levels down. It also does not stop when you navigate elsewhere; the walk that a moment's hover started keeps running while you are already reading somewhere else.
Nothing on the drive's side can prevent this. Explorer decides it wants the size before it touches the file system at all, and what it then sends are ordinary directory listings, indistinguishable from the ones an open window asks for. Windows' own WebDAV redirector behaves exactly the same way, so this is not a property of how the drive is mounted.
The dialog is called Folder Options, and what it is named in Windows' own search depends on your display language. The command below does not:
control.exe /name Microsoft.FolderOptions
Run it from Win+R or a command prompt. Microsoft.FolderOptions is the canonical name Windows registers for that dialog, the same on every installation whatever the language. Through the interface it sits in Control Panel, under Appearance and Personalization.
Switch to the View tab and, under Advanced settings, clear the box:
Display file size information in folder tips
Click OK. Folder tips still appear, they simply no longer carry a size.
The same switch in the registry, for anyone who would rather set it there:
| Key | HKCU\Software\Microsoft\Windows\CurrentVersion\Explorer\Advanced |
| Value |
FolderContentsInfoTip, REG_DWORD
|
| Data |
1 = on (the default), 0 = off |
Explorer picks the change up immediately — no sign-out, no restart of explorer.exe.
reg query "HKCU\Software\Microsoft\Windows\CurrentVersion\Explorer\Advanced" /v FolderContentsInfoTip
reg add "HKCU\Software\Microsoft\Windows\CurrentVersion\Explorer\Advanced" /v FolderContentsInfoTip /t REG_DWORD /d 0 /f
ShowInfoTip sits in the same key and is a different switch: it turns folder and file tooltips off altogether. Leave it alone unless that is what you want.
Important
The setting belongs to your Windows account and applies to every drive, local disks included. What you give up is the size shown in the tooltip. A folder's Properties page still calculates it, on demand, when you ask for it.
This is background activity, not a stall — you are unlikely to see a window freeze because of it. What it costs is the drive's attention: while the walk is running, its requests stand in the same queue as the listing you are actually waiting for.
Whether it is worth turning off depends on where your server is. On a fast local network the walk finishes before you notice it. Over the internet, where a single listing takes a few hundred milliseconds, a hover of one second can occupy the drive for the next half minute. The way to see the difference is to turn the setting off and repeat the same browsing.
See also TortoiseGit, which is the same kind of problem from a different program: something other than your window asking the drive questions about folders you are not looking at.
