YAML Configuration

This page is intended to fully document all configuration options available in the stack.yaml file. Note that this page is likely to be both incomplete and sometimes inaccurate. If you see such cases, please update the page, and if you’re not sure how, open an issue labeled “question”.

The stack.yaml configuration options break down into project specific options in:

  • <project dir>/stack.yaml

and non-project specific options in:

  • /etc/stack/config.yaml – for system global non-project default options
  • ~/.stack/config.yaml – for user non-project default options
  • The project file itself may also contain non-project specific options

Note: When stack is invoked outside a stack project it will source project specific options from ~/.stack/global/stack.yaml. Options in this file will be ignored for a project with its own <project dir>/stack.yaml.

Project config

Project specific options are only valid in the stack.yaml file local to a project, not in the user or global config files.


(Mercurial support since

This lists all local packages. In the simplest usage, it will be a list of directories, e.g.:

- dir1
- dir2
- dir3

However, it supports three other location types: an HTTP URL referring to a tarball that can be downloaded, and information on a Git or Mercurial repo to clone, together with this SHA1 commit. For example:

- some-directory
- https://example.com/foo/bar/baz-0.0.2.tar.gz
- location:
    git: git@github.com:commercialhaskell/stack.git
    commit: 6a86ee32e5b869a877151f74064572225e1a0398
- location:
    hg: https://example.com/hg/repo
    commit: da39a3ee5e6b4b0d3255bfef95601890afd80709

Note: it is highly recommended that you only use SHA1 values for a Git or Mercurial commit. Other values may work, but they are not officially supported, and may result in unexpected behavior (namely, stack will not automatically pull to update to new versions).

stack further allows you to tweak your packages by specifying two additional settings:

  • A list of subdirectories to build (useful for mega-repos like wai or digestive-functors)
  • Whether a package should be treated as a dependency: a package marked extra-dep: true will only be built if demanded by a non-dependency, and its test suites and benchmarks will not be run. This is useful for tweaking upstream packages.

To tie this all together, here’s an example of the different settings:

- local-package
- location: vendor/binary
  extra-dep: true
- location:
    git: git@github.com:yesodweb/wai
    commit: 2f8a8e1b771829f4a8a77c0111352ce45a14c30f
  - auto-update
  - wai


This is a list of package identifiers for additional packages from upstream to be included. This is usually used to augment an LTS Haskell or Stackage Nightly snapshot with a package that is not present or is at an older version than you wish to use.

- acme-missiles-0.3


Specifies how dependencies are resolved. There are currently four resolver types:

  • LTS Haskell snapshots, e.g. resolver: lts-2.14
  • Stackage Nightly snapshot, e.g. resolver: nightly-2015-06-16
  • No snapshot, just use packages shipped with the compiler
    • For GHC this looks like resolver: ghc-7.10.2
    • For GHCJS this looks like resolver: ghcjs-0.1.0_ghc-7.10.2.
  • Custom snapshot

Each of these resolvers will also determine what constraints are placed on the compiler version. See the compiler-check option for some additional control over compiler version.


Flags can be set for each package separately, e.g.

    flag-name: true

Flags will only affect packages in your packages and extra-deps settings. Packages that come from the snapshot global database or are not affected.


The image settings are used for the creation of container images using stack image container, e.g.

    base: "fpco/stack-build"
      static: /data/static

base is the docker image that will be used to built upon. The add lines allow you to add additional directories to your image. You can also specify entrypoints. Your executables are placed in /usr/local/bin.

Non-project config

Non-project config options may go in the global config (/etc/stack/config.yaml) or the user config (~/.stack/config.yaml).


See Docker integration.



See Nix integration.


Integer indicating how many simultaneous downloads are allowed to happen

Default: 8


Strip out the “Loading ...” lines from GHC build output, produced when using Template Haskell

Default: true


URL providing a JSON with information on the latest LTS and Nightly snapshots, used for automatic project configuration.

Default: https://www.stackage.org/download/snapshots.json


Target directory for stack install and stack build --copy-bins.

Default: ~/.local/bin


- name: Hackage
  download-prefix: https://s3.amazonaws.com/hackage.fpcomplete.com/package/

  # at least one of the following must be present
  git: https://github.com/commercialhaskell/all-cabal-hashes.git
  http: https://s3.amazonaws.com/hackage.fpcomplete.com/00-index.tar.gz

  # optional fields, both default to false
  gpg-verify: false
  require-hashes: false

One thing you should be aware of: if you change the contents of package-version combination by setting a different package index, this can have an effect on other projects by installing into your shared snapshot database.


Enables or disables using the GHC available on the PATH. Useful to disable if you want to force stack to use its own installed GHC (via stack setup), in cases where your system GHC my be incomplete for some reason. Default is true.

# Turn off system GHC
system-ghc: false


Whether or not to automatically install GHC when necessary. Default is false, which means stack will prompt you to run stack setup as needed.


Should we skip the check to confirm that your system GHC version (on the PATH) matches what your project expects? Default is false.


Require a version of stack within the specified range (cabal-style) to be used for this project. Example: require-stack-version: "== 0.1.*"

Default: "-any"


Set the architecture and operating system for GHC, build directories, etc. Values are those recognized by Cabal, e.g.:

arch: i386, x86_64
os: windows, linux

You likely only ever want to change the arch value. This can also be set via the command line.


A list of extra paths to be searched for header files and libraries, respectively. Paths should be absolute

- /opt/foo/include
- /opt/foo/lib


(Since 0.1.4)

Specifies how the compiler version in the resolver is matched against concrete versions. Valid values:

  • match-minor: make sure that the first three components match, but allow patch-level differences. For example< and would both match 7.8.4. This is useful to allow for custom patch levels of a compiler. This is the default
  • match-exact: the entire version number must match precisely
  • newer-minor: the third component can be increased, e.g. if your resolver is ghc-7.10.1, then 7.10.2 will also be allowed. This was the default up through stack 0.1.3


(Since 0.1.7)

Overrides the compiler version in the resolver. Note that the compiler-check flag also applies to the version numbers. This uses the same syntax as compiler resolvers like ghc-7.10.2 or ghcjs- (version used for the ‘old-base’ version of GHCJS). While it’s useful to override the compiler for a variety of reasons, the main usecase is to use GHCJS with a stackage snapshot, like this:

resolver: lts-3.10
compiler: ghcjs-
compiler-check: match-exact


(Since 0.1.4)

Allows specifying per-package and global GHC options:

    # All packages
    "*": -Wall
    some-package: -DSOME_CPP_FLAG

Caveat emptor: setting options like this will affect your snapshot packages, which can lead to unpredictable behavior versus official Stackage snapshots. This is in contrast to the ghc-options command line flag, which will only affect local packages.


(Since 0.1.5)

Specify a variant binary distribution of GHC to use. Known values:

  • standard: This is the default, uses the standard GHC binary distribution
  • gmp4: Use the “centos6” GHC bindist, for Linux systems with libgmp4 (aka libgmp.so.3), such as CentOS 6. This variant will be used automatically on such systems; you should not need to specify it in the configuration
  • integersimple: Use a GHC bindist that uses integer-simple instead of GMP
  • any other value: Use a custom GHC bindist. You should specify setup-info so stack setup knows where to download it, or pass the stack setup --ghc-bindist argument on the command-line


(Since 0.1.5)

Allows overriding from where tools like GHC and msys2 (on Windows) are downloaded. Most useful for specifying locations of custom GHC binary distributions (for use with the ghc-variant option):

        url: "https://example.com/ghc-7.10.2-i386-unknown-mingw32-foo.tar.xz"


(Since 0.1.5)

When using the sdist and upload commands, this setting determines whether the cabal file’s dependencies should be modified to reflect PVP lower and upper bounds. Values are none (unchanged), upper (add upper bounds), lower (add lower bounds), and both (and upper and lower bounds). The algorithm it follows is:

  • If an upper or lower bound already exists on a dependency, it’s left alone
  • When adding a lower bound, we look at the current version specified by stack.yaml, and set it as the lower bound (e.g., foo >= 1.2.3)
  • When adding an upper bound, we require less than the next major version (e.g., foo < 1.3)
pvp-bounds: none

For more information, see the announcement blog post.


(Since 0.1.6)

Modify the code page for UTF-8 output when running on Windows. Default behavior is to modify.

modify-code-page: false


(Since 0.1.6)

Decide whether a custom Setup.hs script should be run with an explicit list of dependencies, based on the dependencies of the package itself. It associates the name of a local package with a boolean. When it’s true, the Setup.hs script is built with an explicit list of packages. When it’s false (default), the Setup.hs script is built without access to the local DB, but can access any package in the snapshot / global DB.

Note that in the future, this will be unnecessary, once Cabal provides full support for explicit Setup.hs dependencies.

    "*": true # change the default
    entropy: false # override the new default for one package


(Since 0.1.6)

Should we rebuild a package when its GHC options change? Before 0.1.6, this was a non-configurable true. However, in most cases, the flag is used to affect optimization levels and warning behavior, for which GHC itself doesn’t actually recompile the modules anyway. Therefore, the new behavior is to not recompile on an options change, but this behavior can be changed back with the following:

rebuild-ghc-options: true


(Since 0.1.6)

Which packages do ghc-options on the command line get applied to? Before 0.1.6, the default value was targets

apply-ghc-options: locals # all local packages, the default
# apply-ghc-options: targets # all local packages that are targets
# apply-ghc-options: everything # applied even to snapshot and extra-deps

Note that everything is a slightly dangerous value, as it can break invariants about your snapshot database.


(Since 0.1.7)

Ignore version bounds in .cabal files. Default is false.

allow-newer: true

Note that this also ignores lower bounds. The name “allow-newer” is chosen to match the commonly used cabal option.


Templates used with stack new have a number of parameters that affect the generated code. These can be set for all new projects you create. The result of them can be observed in the generated LICENSE and cabal files.

The 5 parameters are: author-email, author-name, category, copyright and github-username.

  • author-email - sets the maintainer property in cabal
  • author-name - sets the author property in cabal and the name used in LICENSE
  • category - sets the category property in cabal. This is used in Hackage. For examples of categories see Packages by category. It makes sense for category to be set on a per project basis because it is uncommon for all projects a user creates to belong to the same category. The category can be set per project by passing -p "category:value" to the stack new command.
  • copyright - sets the copyright property in cabal. It is typically the name of the holder of the copyright on the package and the year(s) from which copyright is claimed. For example: Copyright: (c) 2006-2007 Joe Bloggs
  • github-username - used to generate homepage and source-repository in cabal. For instance github-username: myusername and stack new my-project new-template would result:
homepage: http://github.com/myusername/my-project#readme

source-repository head
  type: git
  location: https://github.com/myusername/my-project

These properties can be set in config.yaml as follows:

    author-name: Your Name
    author-email: youremail@example.com
    category: Your Projects Category
    copyright: 'Copyright: (c) 2015 Your Name'
    github-username: yourusername