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c#.netwindows-10filesystemsntfs

What actions update LastAccessTime?

Obviously not every action on a file or folder will immediately update its LastAccessTime since that just means that checking what is its LastAccessTime will always return the current time.

But what is the limit? What can be done without changing an item's LastAccessTime?

I checked the docs, but it's not mentioned there.

(You might have heard that LastAccessTime isn't updated anymore. This information is outdated. AFAIK Windows 10 and 11 now do update it.)

Solution

  • According to this although reading a file, writing to a file and running (in case of executables) would change the LastAccessTime so it may be translated in to lots of user actions such as:

    • Accessing the file to generate a preview or thumbnail image.
    • Accessing the file to show its property sheet.
    • Accessing the file to retrieve its icon.
    • Accessing the file to retrieve properties to show in Explorer or some other viewer.
    • Accessing the file in order to back it up.
    • Accessing the file in order to display its context menu, something you aren’t supposed to be doing in the first place but people do it anyway.

    The main article also describes a way to read without updating the attribute. Also mention that from windows 10 1803 and above The LastAccessTime updates are enabled for NTFS volumes when the size of the system volume is 128 GB or less although you can enable it (see here). But again from 20H1 onward the option is turned on by default regardless of the system volume size!