Kustomize versus Helm: What's the difference?

When it comes to managing and deploying Kubernetes applications, two tools consistently stand out: Kustomize and Helm. Both simplify the complexity of Kubernetes deployments, but they take fundamentally different approaches to solving the same challenge.

Helm is a package manager for Kubernetes that bundles everything needed for an application into a single, reusable package called a Helm chart. Kustomize, a Kubernetes-native tool, takes a declarative approach by using patches and overlays to modify base configurations that require the use of templating languages.

The choice between these tools isn’t just a technical preference—it directly impacts development team productivity, operational costs and the ability to scale applications reliably. Many organizations discover significant value in using both tools together, but understanding when and why to choose each approach is essential for building an effective, scalable Kubernetes deployment and management strategy.

Before exploring Kustomize and Helm, it’s helpful to understand containerization, which is the foundation of modern cloud-native applications.

Containerization packages applications with everything needed to run—code, libraries and configuration—into lightweight, portable units called containers, which typically run on Linux-based systems. This process enables software to run consistently across various environments, from developer laptops to production cloud infrastructure.

Kubernetes, also known as k8s or kube, orchestrates containers (typically Docker-based) at scale by automating deployment, scaling and resource management across clusters of machines.

According to a 2024 survey from the Cloud Native Computing Foundation’s (CNCF), cloud-native adoption has reached an all-time high of 89% among surveyed organizations, and 93% of organizations are using, piloting or evaluating Kubernetes.¹

As organizations move from simple applications to complex, multiservice architectures, the configuration files required to manage Kubernetes deployments become increasingly complex. A typical enterprise application might require dozens of configuration files, each needing customization for different environments—development, staging and production.

 This complexity creates several business challenges:

• Difficulty maintaining consistency across environments

• Higher operational expenses

• Lack of deployment automation, which causes manual errors

• Longer time-to-market for new features

Both Kustomize and Helm were created to address these challenges, but they take distinctly different approaches. Helm entered the market first when Deis (later acquired by Microsoft) introduced it as one of the earliest tools designed to simplify Kubernetes application management. The project gained further credibility when Deis donated it to the CNCF in 2018, and it achieved full CNCF graduation status in 2020.

Meanwhile, Kubernetes took a different path by integrating Kustomize directly into the kubectl command-line interface (CLI) with the release of Kubernetes 1.14 in 2019.

Kustomize employs a declarative configuration management approach. Rather than scripting how to achieve a specific state, DevOps and other teams describe what they want their final configuration to look like. 

The tool uses a “base and overlay” methodology. Teams maintain a standard base configuration that captures the core characteristics of their application. Then, for each environment or variant, they create overlays that specify only the differences needed for that specific context.

Consider a base configuration that defines a web application with standard resource requirements and a basic networking setup. A development overlay might reduce resource limits and replicas to save costs, while a production overlay might increase security settings and add monitoring components. Kustomize merges these configurations to produce the final deployment Kubernetes manifests (YAML or JSON files) that describe the wanted state of Kubernetes resources.

Kustomize works directly with native YAML manifest files (such as deployment.yaml) that contain standard Kubernetes fields like apiVersion. This approach eliminates the need for a templating language, making it easier for teams to adopt without learning more coding syntax beyond standard Kustomize YAML configurations. As a result, teams can quickly implement sophisticated configuration management while working with the familiar Kubernetes YAML syntax they already know.

The most popular Kubernetes package manager on the market, Helm functions essentially as an app store for Kubernetes applications, managing and installing prepackaged applications with ease. According to recent CNCF surveys, Helm leads as the preferred Kubernetes package manager, with 75% adoption among organizations running Kubernetes.²

Helm packages applications into "Helm charts," which are collections of pre-configured Kubernetes resources that teams can install, upgrade and manage as a single unit. Each chart includes configuration files (such as chart.yaml) and uses Go templates to enable dynamic configuration based on input values.

The advantage of Helm lies in its templating engine and package management capabilities. Instead of maintaining multiple versions of similar configurations, Helm enables teams to create charts with placeholders and use separate value files (such as values.yaml) to populate those placeholders during deployment. Teams can use helm template to preview the final rendered configuration before applying it to the Kubernetes cluster.  

Beyond templating, Helm provides comprehensive lifecycle management features, including the ability to roll back deployments, manage releases and track deployment history. These capabilities make Helm valuable for organizations managing complex application portfolios where orchestration and rollback functions are crucial.

For example, an e-commerce company can use one chart for their online store but customize it for different environments—fewer servers for testing, more servers for production—without creating separate configuration files.

To deploy these charts, teams use helm install, which automatically applies all resources to the target Kubernetes cluster through the Kubernetes application programming interface (API). Helm handles versioning and dependency management automatically, ensuring consistent and reliable deployments

The choice between Kustomize and Helm depends on specific deployment challenges and business objectives. Organizations customizing the same application for different environments typically benefit most from Kustomize. Those managing multiple applications or requiring sophisticated deployment controls find Helm more suitable.

The following section goes into further detail on when it is best to use each solution.

Most organizations need to deploy the same application across development, staging and production environments with subtle but significant differences. Kustomize excels in this scenario by allowing teams to maintain a single source of truth while applying environment-specific modifications.

Development environments might require reduced resource limits to save costs, while production environments require enhanced security settings, different ConfigMaps and monitoring components. Kustomize enables organizations to define these differences without duplicating entire configuration files.

Different deployment situations often require different security policies or compliance measures. Kustomize allows teams to layer these requirements onto base configurations without creating entirely separate configuration sets. This capability proves valuable for organizations operating across multiple regions or industries with varying regulatory requirements.

When rolling out configuration changes across large application portfolios, Kustomize enables teams to make incremental modifications without disrupting the entire configuration structure. This approach reduces risk and makes it easier to identify and fix issues such as misconfigurations or deployment failures.

One of Helm's primary advantages is its packaging capabilities, which particularly benefit organizations building platforms or seeking to standardize application deployments across teams.

Teams can create reusable charts that capture best practices and organizational standards, then distribute them across the enterprise.

Applications requiring sophisticated deployment orchestration, such as multistep rollouts, dependency management and rollback capabilities, are well suited to Helm’s release management features. If something goes wrong, Helm can instantly revert to the previous working version, reducing the impact on users.

When integrating popular open source applications or vendor solutions, Helm’s extensive chart repository (chart repo) provides prebuilt packages that can significantly reduce implementation time.

Rather than building configurations from scratch, teams can leverage community-maintained charts for databases, monitoring system continuous integration or continuous delivery (CI/CD) pipelines and other standard IT infrastructure components.

SaaS platforms often use Helm to manage customer-specific deployments of applications, deploying the same application multiple times with different configurations in separate namespaces. This approach provides the isolation and customization needed for multitenant architectures.

Kustomize offers several benefits for Kubernetes configuration management, including:

Organizations choose Helm for benefits like these.

Rather than viewing Kustomize and Helm as competing solutions, many organizations find significant value in using both tools together. This hybrid approach uses the strengths of each tool while mitigating their limitations.

Here are some popular use cases:

• Initial deployment and environment customization

• Third-party applications with custom configurations

• Multi-team environments

A typical joint-use pattern involves implementing Helm for initial application packaging and deployment, followed by the use of Kustomize to apply environment-specific customizations. This approach provides the benefits of Helm’s package management and release capabilities while maintaining the simplicity and transparency of Kustomize for ongoing configuration management.

For instance, an organization might use a Helm chart to deploy a microservices application with all its dependencies. The next step is to use Kustomize overlays to add security policies for production or configure different Kubernetes ingress rules for staging.

Organizations often use Helm for deploying third-party applications from its extensive chart repo, while using Kustomize for custom applications where they want more direct control over configuration management.

This combination enables teams to use community-maintained charts for popular tools—such as monitoring systems or message queues—while maintaining complete control over their proprietary applications.

In large organizations with multiple development teams, platform teams often create standardized Helm charts that contain organizational best practices and compliance requirements. These charts work together with Infrastructure as Code (IaC) tools like Terraform to manage the complete deployment pipeline.

Individual development teams then use Kustomize to customize these charts for their specific applications and environments without modifying the base charts. This approach creates a clean separation that integrates seamlessly with GitOps tools like ArgoCD for automated deployment workflows.

Effective Kubernetes configuration management requires a flexible strategy that adapts to evolving application needs.

Understanding the differences between Helm and Kustomize—and knowing how to integrate them effectively—helps reduce complexity and maintain consistency. This strategic combination ultimately leads to more maintainable and scalable Kubernetes environments.