Haskell Playground is live at play.haskell.org

Dear haskellers,
it is with great pleasure that the Haskell.org Committee is announcing the availability of the Haskell Playground at https://play.haskell.org!

The playground is a work of love by @tomsmeding, now with support from Haskell.org. He deserves all your encouragement!

Now, to the details:

Exposed Packages

Click here to see the list of exposed packages
  • aeson,
  • array,
  • assoc,
  • async,
  • attoparsec,
  • base,
  • base16,
  • base64,
  • bifunctors,
  • binary,
  • bytestring,
  • Cabal,
  • comonad,
  • containers,
  • contravariant,
  • deepseq,
  • directory,
  • distributive,
  • dlist,
  • effectful,
  • effectful-core,
  • exceptions,
  • filepath,
  • generically,
  • ghc-boot,
  • ghc-boot-th,
  • ghc-heap,
  • ghci,
  • ghc-prim,
  • hashable,
  • haskeline,
  • hpc,
  • indexed-traversable,
  • integer-gmp,
  • integer-logarithms,
  • libiserv,
  • monad-control,
  • mtl,
  • parsec,
  • pretty,
  • primitive,
  • process,
  • QuickCheck,
  • random,
  • safe-exceptions,
  • scientific,
  • semialign,
  • semigroupoids,
  • stm,
  • strict,
  • template-haskell,
  • terminfo,
  • text,
  • text-short,
  • th-abstraction,
  • these,
  • time,
  • transformers,
  • transformers-base,
  • unix,
  • unliftio,
  • unliftio-core,
  • unordered-containers,
  • uuid-types,
  • vector,
  • vector-stream,
  • witherable,
  • xhtml

GHC Versions supported

  • 8.6.5
  • 8.8.4
  • 8.10.7
  • 9.0.2
  • 9.2.5
  • 9.4.4

Aaaaand in bonus, thanks to @hasufell’s pre-release channel for ghcup, the two latest alpha releases of GHC 9.6 are available. Especially interesting if you want to compare Core or ASM outputs across compiler versions, test the new TypeData extension. You can even try out the Delimited Continuations.


The playground uses Bubblewrap for sanboxing.


You can perform an API request to the playground like this:

  "code": "main :: IO ()\nmain = print 42",
  "version": "9.2.4",  // or "8.10.7", or "", etc.
  "opt": "O1",  // "O0", "O1" or "O2"
  "output": "run"  // "run", "core" or "asm"

Playground Initialisation

If you wish to provide a link that open a new playground with custom code, you can provide the code url-encoded as the code query parameter, like this:

https://play.haskell.org/?code=main%20%3A%3A%20IO%20() main%20%3D%20putStrLn%20"Hello%20Discourse!"

Happy hacking!


Is the set of available packages final? For little experiments (kinda what tools like this one are well suited) I like to use extra.

Also, vector usually makes more sense if vector-algorithms is available.

The set of available packages is not final at all! I’m not comfortable yet with including all of Stackage, not least because of the disk space and build time requirements. So at least for now, sensible requests like yours are welcome.

In fact if you look again, you’ll see that your suggested packages are now available on all provided GHC versions. :slight_smile:

The full list of available packages is here, which is of course not very convenient to read/find. Making this nicely available in the interface (and fixing synchronisation of package versions across multiple worker machines) is a TODO item.


This is fantastic! Great job, and a great addition to the ecosystem!

Just one suggestion: Maybe it’s possible to start with a simpler example? For Haskell newcomers who have just been patted on the back by a seasoned Haskeller with the words “No worries, you don’t need to understand category theory for this” it’s maybe a bit intimidating to start with import Data.Bifunctor. One could rewrite the example by expanding the first and second functions, or defining toright and toleft with an accumulator argument, …


For other readers: this has been addressed in the course of fixing #23 :slight_smile:


Playground is fantastic!
It’s fun to use.

I have made this in the playground today, surprisingly quickly almost from scratch.
Here is a new better version of it.


Would it be possible to somehow integrate the playground with HLS?

In what way do you imagine that?