Bicep vs ARM Templates for Secure Scalable Azure Landing Zones

In this blog post Bicep vs ARM Templates for Secure Scalable Azure Landing Zones we will explain why infrastructure code that works today can still become an expensive problem tomorrow. If every Azure policy, security or networking change requires someone to edit hundreds of lines of difficult code, your landing zone can quickly become slow, risky and dependent on one or two specialists.

At a high level, infrastructure as code means defining your Azure environment in files rather than building it manually through the Azure portal. Those files can create subscriptions, networks, security policies, access controls and monitoring in a consistent, repeatable way. If you need a broader introduction first, read why your organisation needs an Azure Landing Zone.

The technology behind Bicep and ARM templates

Azure Resource Manager, usually shortened to ARM, is the management service that processes Azure deployments. An ARM template is a JSON file that tells Azure what resources and settings should exist.

Bicep is a Microsoft-developed language that provides a cleaner way to describe the same Azure resources. When you deploy a Bicep file, it is automatically converted into an ARM template before Azure Resource Manager processes it.

This means Bicep is not a competing deployment engine. Both options ultimately use Azure Resource Manager, support repeatable deployments and can be included in automated release pipelines. The biggest difference is how easily people can read, maintain and test the source files.

Why the choice matters for a landing zone

A landing zone is not a one-off Azure setup. It becomes the controlled foundation for every future cloud workload, from business applications and data platforms to virtual desktops and artificial intelligence services.

It commonly includes management groups, which organise subscriptions; Azure Policy, which enforces approved settings; role-based access control, which determines who can do what; shared networking; security monitoring; and cost controls.

If this foundation is difficult to change, teams either wait for the platform team or work around the controls. Both outcomes increase cost and risk.

Bicep is easier to read and maintain

ARM templates use JSON, which requires considerable formatting and repetition. Bicep removes much of that overhead while keeping access to Azure resource types and settings.

For example, the following Bicep code creates a resource group for shared landing zone connectivity:

targetScope = 'subscription'

param location string = 'australiaeast'
param resourceGroupName string = 'rg-platform-connectivity-aue'

resource platformResourceGroup 'Microsoft.Resources/resourceGroups@2022-09-01' = {
 name: resourceGroupName
 location: location
 tags: {
 environment: 'platform'
 managedBy: 'bicep'
 }
}

The equivalent ARM template requires additional schema, parameter, expression and formatting sections. That extra code does not necessarily create more business value. It usually means more material to review, troubleshoot and maintain.

Bicep also provides editor suggestions, validation and clearer error detection. In practical terms, engineers can identify many mistakes before a change reaches Azure, reducing failed deployments and emergency fixes.

Four business reasons to choose Bicep

1. Changes are faster to review

A landing zone change may affect every subscription in the organisation. Reviewers need to understand whether a proposed update will alter networking, permissions, logging or security policies.

Because Bicep is more concise, teams spend less time interpreting syntax and more time assessing business risk. This can shorten approval cycles without weakening oversight.

2. Reusable modules reduce duplicated work

Bicep supports modules, which are reusable packages of infrastructure code. A module might create a standard subscription, apply security policies or configure monitoring the same way every time.

Microsoft also provides Azure Verified Modules, which are tested building blocks for common Azure resources and architectural patterns. These can reduce development time, although every module should still be reviewed against your security, cost and compliance requirements.

This modular approach is particularly useful when building workload environments repeatedly. We use the same principle when helping organisations move from individual migrations to secure Azure landing zones at scale.

3. Security controls become more consistent

Bicep does not make an environment secure by itself. It does, however, make approved controls easier to deploy consistently across multiple subscriptions.

This supports governance programs based on the Essential Eight, the Australian Government’s baseline cybersecurity framework. Infrastructure code can help demonstrate that logging, access restrictions and security services are deployed consistently, but it does not automatically make an organisation compliant.

4. Teams are less dependent on individual specialists

Long and complicated ARM templates often become understood by only their original author. If that person leaves or becomes unavailable, even a small update may turn into a costly investigation.

Bicep makes the intent of the code clearer. Combined with documentation, version control and automated testing, this reduces key-person risk and makes support easier to hand over.

When ARM templates still make sense

ARM templates are not obsolete. They remain fully valid for Azure deployments and may be appropriate when:

• You have a mature ARM template library that rarely changes.
• A Microsoft or software vendor solution generates an ARM template for you.
• Your team has reliable ARM processes and no immediate maintenance problem.
• You need the generated JSON output for auditing or integration purposes.

The important question is not whether ARM still works. It is whether continuing to maintain it is the lowest-risk and lowest-cost option for your organisation.

A complete rewrite is rarely necessary. Bicep tools can convert existing ARM templates into a starting Bicep file, although the result should be reviewed, simplified and tested rather than accepted blindly.

A practical landing zone scenario

Consider an anonymised example based on a common mid-sized environment. A 200-person organisation has several Azure subscriptions and a collection of ARM templates built over multiple projects. Only one senior engineer is comfortable changing them, so routine policy updates wait for that person’s availability.

The organisation does not replace everything at once. It keeps stable legacy templates in place while moving frequently changed components, such as subscription setup, policy assignments and monitoring, into Bicep modules.

New environments become faster to deploy, code reviews become easier, and policy changes can be tested before release. The business outcome is not simply cleaner code. It is less engineering time, fewer deployment errors and a lower chance of inconsistent security controls.

How to migrate without disrupting Azure

1. Inventory your existing templates. Identify which files are actively maintained, duplicated or poorly understood.
2. Start with a low-risk component. Convert a resource group, monitoring configuration or workload module before changing organisation-wide policies.
3. Refactor the converted code. Break large files into reusable modules with clear names, parameters and outputs.
4. Preview every change. Use Azure’s what-if feature to show what will be created, modified or removed before deployment.
5. Deploy through a controlled pipeline. Require peer review, automated validation and approval for production changes.
6. Document ownership. Record who can approve changes, how failures are handled and how previous versions can be restored.

The same repeatable approach can extend beyond the core landing zone. For example, CloudProInc uses Bicep when deploying Azure OpenAI resources and when helping organisations provision Microsoft Foundry environments with stronger AI governance.

Our recommendation for Azure landing zones

For most organisations building a new Azure-only landing zone, Bicep is the practical default. It provides the capabilities of ARM templates in a format that is easier to understand, review and maintain.

Existing ARM templates do not need to be replaced simply because Bicep exists. Prioritise the templates that change frequently, create operational delays or carry the greatest security risk.

CloudProInc brings more than 20 years of enterprise IT experience to this process as a Microsoft Partner and Wiz Security Integrator. Our Melbourne-based team works directly with technology leaders to design practical Azure foundations that control cost, reduce security risk and remain manageable after the initial project is complete.

If you are unsure whether your current ARM templates are helping or holding back your Azure strategy, we are happy to review the setup and identify sensible next steps — no strings attached.