Global spending on cloud infrastructure hit $129 billion in the first quarter of 2026, up more than $35 billion year-on-year, according to Synergy Research Group — the 9th straight quarter in which growth has accelerated. Amazon and Microsoft remain the two names UK CTOs, CIOs and founders weigh up first, holding 28% and 21% of that market between them. Separate research from Flexera's 2026 State of the Cloud Report found that 83% of organisations now run workloads on AWS and 79% on Azure, with most businesses using both to some degree.

That overlap is exactly why the AWS vs Azure application development decision is harder than it looks. For a UK business commissioning a new build, whether that is a customer-facing SaaS product or an internal line-of-business app, the choice of platform shapes monthly infrastructure cost, how new starters get access, and where regulated data physically sits.

This guide compares the two platforms on the five factors that matter most for azure cloud application development UK projects and AWS build alike, works through two anonymised UK projects, and ends with a scenario-based checklist for choosing between AWS and Azure.

What Is AWS, and What Is Microsoft Azure Used For?

Amazon Web Services (AWS) is Amazon's cloud computing platform, providing over 200 different services across compute, storage, databases, and AI. It's used to build, host and scale virtually any application — from a two-person startup's MVP to enterprise platforms handling millions of daily transactions — all without physical hardware.

Microsoft Azure is Microsoft's equivalent cloud platform, designed to integrate with and authenticate through an organisation's existing Microsoft estate. It is commonly used for hosting web applications via App Service, running SQL Server and .NET workloads, and building on Microsoft's AI stack through Azure OpenAI Service — which is why it tends to be the default choice for UK businesses already running Microsoft 365 and on-premises Active Directory.

AWS vs Azure: The Full Comparison for UK App Development

What the Data Says About Who Picks Which

The Flexera figures point to two distinct buyer profiles rather than one platform being a clear winner. For enterprises, the usage of AWS and Azure is almost the same, at 84% and 82% respectively, but the number of enterprises using Azure in experiment mode and planned, at 94%, is ahead of AWS's 92%. For smaller businesses, AWS is clearly preferred: 77% use AWS vs 63% for Azure. Azure's smaller service catalogue and deeper Microsoft integration can be a barrier for teams without an existing Microsoft estate.

The UK, alongside Germany, is one of the two largest cloud markets in Europe, which is also why both providers maintain dedicated in-country regions here rather than relying solely on wider EU coverage.

Decision Checklist: Which Platform Fits Your Scenario

1.     Building an MVP with no existing infrastructure?

AWS's breadth and consumption pricing suit fast, unpredictable scaling better than a platform tied to licences you don't yet hold.

2.     Already running Microsoft 365, on-premises AD or SQL Server?

Azure's Entra ID integration and Hybrid Benefit licensing typically cut both cost and identity complexity.

3.     Need to test multiple AI foundation models before committing?

AWS Bedrock's multi-model API avoids locking into one vendor's model early.

4.     Building specifically on OpenAI's GPT models under enterprise compliance?

Azure OpenAI Service, via Microsoft Foundry, is the more direct route.

5.     Operating in a regulated UK sector with strict data residency rules?

Both eu-west-2 and UK South/UK West qualify; the deciding factor is usually the rest of your infrastructure, not the region itself.

6.     Shipping a cross-platform mobile app using a single toolkit?

AWS Amplify remains the more unified option now that App Centre’s build and distribution features have been retired.

Conclusion

There is no universally correct answer to the AWS vs Azure UK business decision — only the platform that matches the infrastructure, identity setup and compliance position a business already has. Startups and teams without a Microsoft estate tend to get up and running faster on AWS, while enterprises already using Microsoft 365 and on-premises AD and Windows licensing see better value in Azure's integration and licensing benefits.

The decision isn't about which is 'better' — it's about which fits what your business already runs. Before committing budget to either, it is worth mapping the decision against three things: the Microsoft estate you already have (or don't), the data residency rules your sector imposes, and which AI services your product roadmap genuinely needs over the next 12 months — rather than being led by whichever platform's sales team gets there first.