GUID Meaning & Definition

 

By Vangie Beal

A Globally Unique Identifier (GUID) is a unique ID that is computed by Windows and Windows applications. It’s a 128-bit number used to identify user accounts, documents, software, hardware, database entries, sessions, and other items. For example, a website may generate a GUID and assign it to a user’s browser to record and track the session.

GUID may also be referred to as a Universally Unique Identifier (UUID). The two terms are synonymous. GUIDs can be used for:

  • Setting a unique primary key in databases
  • Setting a unique filename for uploaded files
  • Setting a unique name for resources
  • Creating and registering unique IDs without contacting a central authority

A GUID follows a specific structure defined in RFC 4122 and comes in multiple formats. However, all variants follows the same structure:

xxxxxxxx-xxxx-Mxxx-Nxxx-xxxxxxxxxxxx

M represents the version. N represents the variant.

Types of GUIDs

The general types of GUIDs include:

  • Random: Uses a system to generate a random, 128-bit number
  • Time-based: Creates a GUID based on the current time
  • Hardware-based: Makes a GUID with certain portions based on hardware features, such as the MAC address of a network card.
  • Content-based (MD5 or SHA-1 hash of data): Creates a GUID based on a hash of the file contents. Files with the same contents will be assigned the same GUID.

Creating a GUID

To create a GUID, there are a multitude of online GUID generators, such as guidgenerator.com. In addition, there are also GUID libraries for programming languages such as PHP, Ruby, and Python.

 

 

Abby Dykes
Abby Dykes
Abby Dykes is a newly-graduated writer and editor for websites such as TechnologyAdvice.com, Webopedia.com, and Project-Management.com. When she’s not writing about technology, she enjoys giving too many treats to her dog and coaching part-time at her local gym.

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