What is Public cloud?

When most people outside the IT industry talk about cloud computing, it’s normally public cloud that they have in mind. Put simply, a public cloud is a form of computer service that is being offered by a third party through an internet connection.

Some public cloud offerings are well-known. For instance, Google offers a whole suite of products – Google Docs, Google Workplace, even Gmail – that fit the bill. Still, when the phrase public cloud is used, it’s generally taken to mean the type of service provided to run businesses.

Public clouds offer a contrast to private clouds, which also provide services via a network connection but are restricted to users within a single organisation (or, possibly, partners of that organisation).

There are three basic type of cloud services. Infrastructure as a service (IaaS), platform as a service (PaaS) and software as a service (SaaS). All three could be offered as part of a public cloud service.

How public clouds work

Large cloud providers, often referred to as hyperscalers, operate large numbers of data centres across the world. Such geographic spread is important so that users aren’t faced with latency issues and can connect to a data centre close to where they operate.

By opting for a public cloud, businesses are spared a lot of the effort and expense of managing a data centre, both in terms of personnel and equipment.

Public cloud architectures

There are two basic forms of public cloud, both of which have their benefits and downsides.

A shared public cloud service, often called a multi-tenant cloud, means that the provider’s servers will be accessed by any number of users, providing access via virtual machines. This means that, in theory, one server could host data from two competitors. In such circumstances, it is incumbent on the operator to keep the data secure.

There is also the possibility of a dedicated public cloud. Here, users log into a server that is dedicated solely for their use. A single tenant service grants greater peace of mind over security and better performance but will cost more.

There is also the issue that companies don’t always know what their computing or storage demands will be. One of the key benefits of cloud computing is that it can offer additional service on-demand. 

Public cloud issues

The main concern for any user opting for the public cloud is that it is in the hands of a third-party supplier. That means data is being handled elsewhere, which could have data governance issues. Users must be aware whether there are any breaches of GDPR (or any other data protection regulation) as the cloud customer is ultimately responsible.

As previously mentioned, security will be a concern. Cloud providers spend heavily on security hardware and software and invest a good deal in recruiting cyber professionals. A provider with a poor record on security won’t last very long.

And, of course, there are the servers themselves: how robust and effective are they? The best cloud providers invest heavily in the fastest servers, and in many cases they install custom-made equipment.

Underpinning all of this is the need for tight service level agreements, ensuring what delivery standards are met. That is, the levels of security and what will happen if things go wrong.


  • A public cloud is a service offered by a third party through an internet connection. 
  • There are three basic types: infrastructure as a service (IaaS), platform as a service (PaaS) and software as a service (SaaS). 
  • A multi-tenant cloud means that the provider’s servers will be accessed by any number of users, providing access via virtual machines. 
  • A single tenant service offers greater security and better performance but will cost more.. 

For more resources on cloud computing

You might be interested in reading our explainers “what is multicloud” and “what is hybrid cloud“, as well as our latest feature outlining lessons from 17 years of cloud computing.

In addition, check out our cloud section.

Maxwell Cooter
Maxwell Cooter

Although Max trained to be a programmer, he quickly found his vocation in journalism. He was the founder editor of Cloud Pro, the UK's first dedicated cloud publication and has written for dozens of titles, including The Guardian and The Daily Telegraph. At TechFinitive he writes about cloud computing and data.