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When doing a backup of my Windows hard drive, I noticed some file names that had a bunch of seemingly random numbers in them. For example: .{ED7BA470-8E54-465E-825C-99712043E01C}

Does that mean something special in Windows? What is the purpose of these files?

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Others have mentioned that ED7BA470-8E54-465E-825C-99712043E01C is a GUID, which is true... but doesn't answer the question.

If you create a folder with the name-format FolderName.{SomeGUID}, Windows will treat the folder as a shortcut and search for the GUID as a CLSID within the Windows registry. Microsoft calls these folders junction points.

What that CLSID looks like from the registry
A CLSID entry (source)

The specific GUID you mentioned is the famous God Mode Shortcut, which brings you to a more powerful version of the Control Panel.

The "God Mode" shortcut
The "God Mode" shortcut (source)

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    I think it would be more accurate to say that Explorer will treat the folder as a shortcut and not Windows, unless the standard kernel32 file APIs also redirect on it? – MicroVirus Oct 29 '15 at 0:42
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    @MicroVirus The Shell API does, the lower API does not. – CodesInChaos Oct 30 '15 at 10:35
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{ED7BA470-8E54-465E-825C-99712043E01C}

Does that mean something special in Windows?

It's a GUID (Globally Unique Identifier).

Because it is a unique string we can be sure that no two backup are generated with the same name.


RFC 4122 - A Universally Unique IDentifier (UUID) URN Namespace

This specification defines a Uniform Resource Name namespace for UUIDs (Universally Unique IDentifier), also known as GUIDs (Globally Unique IDentifier). A UUID is 128 bits long, and can guarantee uniqueness across space and time. UUIDs were originally used in the Apollo Network Computing System and later in the Open Software Foundation's (OSF) Distributed Computing Environment (DCE), and then in Microsoft Windows platforms.

Source A Universally Unique IDentifier (UUID) URN Namespace


GUID's – Global Unique Identifiers

GUID’s are essentially a way to identify an object. However they also name that object uniquely so that no other object has the same GUID.

Now, these "objects" can be anything from an application, part of the operating system or a physical device like a graphics card to the actual computer itself.

Why do we need GUID's..?

Well it is a good idea to define every object on the computer with a unique identifier (GUID). This is because it is possible to have two objects on your computer that have the same "name." So by giving both these objects a unique identifier the computer can distinguish between them.

Both the Windows operating system and software applications that run on your computer, require EVERY object referenced in the Registry to have a unique identity.

Programmers use applications like GUIDGEN.EXE to create these special identifiers, whereas Windows creates them internally.

The GUID concept is based on the Universally Unique Identifiers (UUIDs) defined by the Open Software Foundation (OSF) as part of the Distributed Computing Environment (DCE) - but that is probably more than you wanted to know!

Just remember:..

No matter how many GUID's are created they are ALWAYS unique!

So what do GUID's look like?

Well they are what is called "hexadecimal" numbers - a human-friendly representation of binary coded values.

Essentially each GUID is made up of 5 groups of characters. Each group has a set (block) number of characters as follows: 8, 4, 4, 4, and 12. For example: B96073C9-0E9E-406F-B4A6-620E06242B20


Further Reading

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    …except that social security numbers are mostly deterministic (and the last segment, which only stopped being deterministic in June of 2011, is often requested and given far more freely than it should be) and random GUIDs are mostly random, having only six bits that aren't. – Blacklight Shining Oct 29 '15 at 0:14
  • @BlacklightShining Good point. I will remove that bit of the answer ;) – DavidPostill Oct 29 '15 at 0:19
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A few comments that, together, may possibly constitute an answer:

  1. Not every file on your hard disk is intended for human use. There are plenty of files that are there because they're required for the correct operation of your computer. Disturbing them (deleting, renaming or moving) can have unknown, arbitrary consequences depending on exactly what files and what their purpose is.

  2. The "hex codes" you're referring to are Globally Unique Identifiers (GUIDs). These are basically 128-bit random numbers represented as the characters 0-9 and A-F (base 16). Programs use GUIDs when they want to assign a tag or identifier to something, but want a very very high chance that the identifier they pick is unique. "Globally unique" in "Globally unique identifier" refers to the fact that there is a mathematically almost-guaranteed probability that any random 128-bit number you draw is going to be unique (meaning, no one has ever used that number as a GUID before). GUID collisions can happen, but it's extraordinarily rare. Several times less rare than a cat coming up to you right now and starting to teach you Calculus.

Note: If a cat did come up to you and start explaining Calculus as you read this message, please be aware that you have just traveled into another dimension where the ordinary laws of physics may not necessarily apply. Please watch out for flying pigs; they can hurt if they run into you.

  1. Without knowing exactly where the files you're referring to are located on disk, and how they were generated, it's difficult to speculate about exactly what they're used for. You can usually get an intuitive sense of what they might be by looking at the directory structure they're buried inside; for example, if they're in C:\Windows\Microsoft.NET, they're probably a part of the .NET Framework. And so on.

  2. In the end, unless you're planning to do something with these files, it's probably best to leave them alone. Back them up as usual when you make full backups of your disk, and restore them normally. Just accept the fact that there are going to be thousands of files on your disk that programs or Windows are using to keep your system operating correctly, and it's not necessary to understand their purpose or behavior unless something breaks, in which case you might need to manually intervene and fix something.

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    “it's not necessary to understand their purpose or behavior unless something breaks” — this may be, but curiosity as to how systems work and what odd-seeming files are for is a good thing, is it not? As you said, it's generally a good idea not to mess with e.g. things in system directories, but (contrary to popular belief amongst calculus cats) simply asking about them is quite harmless. – Blacklight Shining Oct 29 '15 at 0:22
  • *fly into you :D – rahuldottech Oct 31 '15 at 15:35
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They are unique identifiers. So unique that only rarely can you find out what application they belong to or why they are present on your computer. It is like a code. Their very nature is secretive. Therefore, you never know if they are necessary, dangerous, or the blinking thing that is causing the problems on your system that you are trying to track down.

  • Welcome to Super User! This duplicates another answer and adds no new content. Please don't post an answer unless you actually have something new to contribute. – DavidPostill Dec 3 '16 at 12:06

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