Windows Explorer Thumbnail View Limit

When viewing files in thumbnail mode in Windows Explorer, there is a limit. In Windows XP, Explorer can only show thumbnails for up to 4,096 (4K) files. After that, files begin showing either a completely white image or the icon of the program associated with that file-type.

Which files are given a thumbnail or not is determined by the order in which they are displayed. For example, if a folder containing 5,096 files is put in thumbnail mode and the first 2,048 files are viewed, then End is pressed and the list is scrolled up, the first and last 2,048 files are given a thumbnail and the middle 1,000 files are left blank. (Of course if the list is scrolled around with the scroll-bar, then seemingly “random” blocks of files here and there may be left blank.)

(There may or may not be a limit in Windows 7 as well. A test will be done and results will be added.)

Windows Explorer Freezes on Folder Access

If Windows Explorer seems to freeze for a few seconds (or a few minutes) whenever a folder, especially top-level folders, are selected, then it could be XP’s auto-sensing feature that is to blame.

Windows XP introduced a feature that peeks inside a folder to determine what the predominate filetype is and provide file-specific tasks for it. For example, if it finds that there more picture files in the folder than anything else, then it will place tasks such as “Print pictures” and “Order prints online” in the Common Tasks pane to the left. It will also place a graphic watermark indicating the “folder type” in the bottom-right of the folder.

This feature is debatable because it has limited use since most people have other ways and programs to do these common tasks. Worse still, if a root folder somehow becomes tagged as a special folder, then all of its subfolders are scanned every time that it is selected, which is what causes the freezing.

Fortunately it is easy to fix. Open a folder that is not “special”, that is, open any folder whose common tasks pane displays “File and Folder Tasks” and has no watermark. Now click the Tools menu and select Folder Options. Click the View tab and then the Apply to All Folders button (then OK). This sets all folders to be the same as the current folder (non-special).

You should now be able to click any folder without it freezing for a while.

As a furtherance to this task, you could also set up other aspects of the folder to be exactly like you wish before clicking Apply to All Folders. This way, all folders will have the same columns, view setting, common task layout, and other attributes that you desire since they will anyway.

(As a side note, it seems that the delay is compounded by the presence of LNK files (Windows shortcuts) and URL files (IE bookmarks)—and possibly PIF files (DOS shortcuts)—in the subfolders as removing them eliminates, for the most part, the freezing. Broken shortcuts increase the delay as do bookmarks to FTP sites. No explanation as to why they affect common tasks has been found.)

Windows Explorer File Sort

Windows Explorer allows you to sort the files and directories in a folder by various properties by clicking the appropriate column header. Folders always come before files regardless of name, and there is unfortunately no way to change this even though sometimes it is desirable to sort with mixed folders/files.

The algorithm for sorting by name is mostly straightforward but with some bumps. Knowing the sort order allows you to choose characters to use as the first character in a file or folder name to control sorting, for example when creating a filing system.

For the most part, the algorithm sorts files/folders by name according to their ASCII values, expect that case is ignored because on Windows, filenames are case-insensitive, that is “MYFILE”, “MyFile”, and “myfile” are all the same file—iirc NTFS can do case-sensitive but it’s actually a hack (mapping).

You should also be aware that numbers are treated as numbers and not strings. For example “123blah” will come after “2blah” since 123 is bigger than 2, even though “1”-“2”-“3” comes before “2”. This behavior can be changed with the NoStrCmpLogical option of the Explorer policies (set HKEY_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion\Policies\Explorer\NoStrCmpLogical to dword:00000001).

Another bump in the algorithm is that the following characters appear out of order: +, <, and > They come after all other characters, in this order. Also, and are ignored altogether when they are the first character.

Here is a list of characters in the order that they will be sorted when used as the first character:

1 – Not (normally) allowed as a filename character
2 – Not in ASCII order
3 – Not used in sort when first character
* 1
/ 1
: 1
? 1
\ 1
| 1
+ 2
< 1,2
= 1
> 1,2

This knowledge will be used in a later article to create a filing system that will allow organization of files and folders since Windows doesn’t really have symbolic links and WinFS has been cancelled until at least Windows Vienna.