Modular Releases Mojo Compiler and Toolchain Under Apache 2.0

The closed compiler opens

Modular announced on August 18, 2026 that the Mojo programming language is fully open source under the Apache 2.0 licence with LLVM exceptions. Source code for the compiler, tooling and other components required to build the language is now available in the company’s main GitHub repository.

The move follows the release of Mojo 1.0 one week earlier, a milestone Modular described as providing source stability. Mojo had been developed for four years with an open community but a closed compiler. During that period, the company released the standard library, tools, support material and hundreds of thousands of lines of kernel code before opening the compiler itself.

Modular presents Mojo as a general-purpose language designed to use GPUs, AI accelerators and other advanced computing hardware. Its licence choice is intended to permit broad adoption and distribution. The LLVM exceptions extend the Apache terms for binaries built with the language, according to the announcement.

The release changes what developers can inspect and build locally. After cloning the repository, contributors can use a Bazel command with the `build-mojo` configuration to compile the Mojo compiler and standard library from source. Modular uses Bazel to coordinate the project’s build steps and caching.

Source access before open contributions

A second configuration, `prebuilt-mojo`, downloads the latest nightly compiler binary for people who are not modifying the compiler, reducing build time. A prebuilt Mojo compiler is still required when customizing MAX kernels or models, the company said. Developers changing the compiler or standard library can run the project’s test suite against their local code.

Opening a repository does not mean every part will immediately accept outside patches. The Mojo standard library has received contributions since 2024, but Modular is not yet accepting contributions to the compiler and tooling. It aims to begin doing so by the end of 2026 and said it will provide more information later.

The company attributed that staged approach to the need for deliberate contribution management, particularly as AI-assisted coding becomes more common. It argues that a compact design team can establish a language’s direction while public feedback helps prevent insular decisions. That is Modular’s stated development philosophy rather than an independently tested advantage.

For users, the immediate distinction is between visibility and governance. The full implementation can now be read, built and modified under a permissive licence, even though the upstream project is not ready to merge external compiler or tooling contributions. The forum remains the channel Modular recommends for questions and for sharing projects.

Mojo’s open-source release therefore completes a sequence rather than beginning one: library and kernel code came first, version 1.0 established the latest language milestone, and the compiler and toolchain now join the public codebase. The next promised step is to open the contribution process further as the implementation matures.