Assembly Line

Pkl

A configuration as code language with rich validation and tooling.

Pkl is an open-source programming language project on GitHub under the Apache-2.0 license (permissive), with 12k stars. It is built with JDK and Kotlin. Its last push was today.

Stars
12k
License
Apache-2.0
Activity
Active
Latest release
0.32.2

Code on GitHub Website

Judgement

What it is
Developer tool
What it does
Apple's configuration-as-code language with types, validation and templates that generates JSON, YAML and property files, with bindings for Java, Kotlin, Swift and Go.
Adopt it when
Your configuration has grown large enough that plain YAML causes mistakes and you want validated, reusable config.
Watch out
Pre-1.0 and less widely adopted than CUE or Jsonnet.
Ready for
Usable
Runs as
Command line and library
Built with
Java and Kotlin
How established
Established: started 2 years ago, latest release 0.32.2.
What the license allows
You can build it into a product you sell, as long as you keep its copyright notice.

Judged on 2026-11-03 from the project's README and GitHub data. The license and age lines are worked out directly.

Built from

JDKKotlin

Follow it down: Pkl → JDK → LLVM project → runs on a microchip

How compilers were built, back to punched paper tape

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Stars, license and activity come from GitHub and refresh on a rolling hourly schedule. The project's own description is quoted as written.