Buildpacks

YAML files dominate configuration in the cloud-native ecosystem. They’re used by Kubernetes, Helm, Tekton, and many other projects to define custom configurations and workflows. But YAML has its oddities, which is why the Cloud Native Buildpacks project chose TOML as its primary configuration format.

What is TOML?

TOML stands for Tom’s Obvious, Minimal Language. It’s a configuration file format created to be simple, readable, and predictable. Designed for humans first and machines second, TOML avoids syntactic ambiguity and is easy to understand even at a glance.

The format uses a key-value structure and supports sections, arrays, and nested tables. Its goal is to be as clear and minimal as possible while still expressive enough for most configuration tasks. Unlike JSON, TOML allows comments. Unlike YAML, it doesn’t rely on indentation for structure, which reduces the likelihood of formatting errors.

TOML has gained adoption in modern developer tools. The Rust package manager Cargo and the Python dependency tool Poetry both use TOML. In the cloud-native ecosystem, containers and Cloud Native Buildpacks also rely on TOML for configuration.

What is a TOML file?

A TOML file is a plain text file with a .toml extension that stores structured configuration data using TOML syntax. It defines settings using simple key-value pairs, and organizes related settings using headers and tables.You can learn more about TOML from the official documentation, but a simple buildpack TOML file looks like this: