- Project plans
- Project activities
- Legislation and standards
- Industry context
Last edited 07 Jun 2017
Global Unique IDs (GUIDs)
Global Unique IDs (GUIDs, sometimes referred to as universally unique identifiers or UUIDs) are 128-bit numbers used to identify digital information, helping to reference them unambiguously. They are similar to the ISBN numbers used for books.
Because they are so large, GUIDs are virtually guaranteed to be unique. They are formatted in a well-defined sequence of 32 hexadecimal digits grouped as 8-4-4-4-12. This provides roughly 10^38 numbers. An example of how a GUID looks in hexadecimal:
The probability of any two GUID's being the same is very low.
GUIDs can be used to identify information about anything, such as products, papers, webpages, etc.
The general types of GUIDs are:
- Random: A random-number generator creates a 128-bit number.
- Time-based: Based on the current time.
- Hardware-based: Certain parts of the GUID are based on the hardware features, although this removes part of the anonymity of the number.
- Content-based: Based on a hash of the file contents. This can be used if duplicate files need to have the same GUID.
Some of the common uses for GUIDs are as follows:
- Unique primary key in databases (allowing database items to be merged without conflict).
- Unique filenames for uploaded files.
- Unique names for resources.
- Unique IDs for products.
- Unique IDs for design files or models.
The advantages of GUIDs are that there is no central authority, and so no need for management. GUIDs can be generated internally and merged from different data sources with a low chance of any conflict.
However, the GUID itself may be larger than the database item it is keeping track of.
 Find out more
 Related articles on Designing Buildings Wiki
Featured articles and news
UK energy policy uncertainty as Welsh project put on hold
What collaborative working achieves and how it can be put in place.
BSRIA publishes the 2019 edition of its small but concise annual databook.
Using QSAND to measure the performance of disaster response.
What U-values are, why they matter and how they are calculated.
The need to ensure that we plan for all aspects of our bio-economy
BSRIA calls on government to reach deeper into the causes of pollution.
George Demetri brings a whole new level of technical knowledge to Designing Buildings Wiki.
Quality professionals need to take an active role in driving the completion process forwards.
The innovations needed to move from rhetoric to realisation.
Creating a sense of place, with radically-low running costs and the highest comfort levels.
A conversation between David Mitchell and Caitlin DeSilvey.