Using Spack in Your Browser

This page lets you explore Spack interactively without installing anything. Click ▶ Run on any block below to start — the spack-lite environment loads on demand in your browser and the same Spack session persists across all blocks on this page.

First run takes ~20 seconds

On the first click, Pyodide (WebAssembly Python), clingo (the ASP solver), and the Spack archive download in the background. Subsequent clicks are instant because the environment stays loaded for the whole page visit.

Getting help

Start by asking Spack what it can do:

$ spack help

Finding packages

List all packages in the seed set (full list loads after a few seconds):

$ spack list

Filter by keyword — try python:

$ spack list python

Package information

Inspect a specific package. hdf5 is a common HPC I/O library:

$ spack info hdf5

zlib is a foundational compression library present in the seed set:

$ spack info zlib

Concretising a spec

spack spec resolves a package specification into a fully concrete dependency tree (versions, variants, compilers). This uses the clingo ASP solver and may take 5–15 s for the first run:

$ spack spec zlib

Try a build variant — HDF5 with Fortran support disabled:

$ spack spec hdf5~fortran

Working with the virtual filesystem

The Spack tree is unpacked into an in-memory filesystem. You can explore it with the built-in shell commands:

$ ls /home/pyodide/spack
$ ls /home/pyodide/spack/var/spack/repos/builtin/packages | head -20

Inspect a package recipe directly:

$ cat /home/pyodide/spack/var/spack/repos/builtin/packages/zlib/package.py

Environment variables

$ env | grep SPACK

Spack configuration

See the fake compiler and package configuration that spack-lite injects so the concretiser has a host environment to target:

$ cat /home/pyodide/.spack/linux/compilers.yaml

$ cat /home/pyodide/.spack/packages.yaml

Loading the full package set

By default only the seed packages are available (fast startup). Run spack load-packages to load all ~8 000 Spack packages in the background:

$ spack load-packages

After loading, try listing a package that isn’t in the seed set:

$ spack list mpich