# 10. Project.toml and Manifest.toml

Two files that are central to Pkg are Project.toml and Manifest.toml. Project.toml and Manifest.toml are written in TOML (hence the .toml extension) and include information about dependencies, versions, package names, UUIDs etc.

Note

The Project.toml and Manifest.toml files are not only used by the package manager; they are also used by Julia's code loading, and determine e.g. what using Example should do. For more details see the section about Code Loading in the Julia manual.

## Project.toml

The project file describes the project on a high level, for example the package/project dependencies and compatibility constraints are listed in the project file. The file entries are described below.

### The name field

The name of the package/project is determined by the name field, for example:

name = "Example"

The name can contain word characters [a-zA-Z0-9_], but can not start with a number. For packages it is recommended to follow the package naming guidelines. The name field is mandatory for packages.

### The uuid field

uuid is a string with a universally unique identifier for the package/project, for example:

uuid = "7876af07-990d-54b4-ab0e-23690620f79a"

The uuid field is mandatory for packages.

Note

It is recommended that UUIDs.uuid4() is used to generate random UUIDs.

### The version field

version is a string with the version number for the package/project. It should consist of three numbers, major version, minor version and patch number, separated with a ., for example:

version = "1.2.5"

Julia uses Semantic Versioning (SemVer) and the version field should follow SemVer. The basic rules are:

• Before 1.0.0, anything goes, but when you make breaking changes the minor version should be incremented.
• After 1.0.0 only make breaking changes when incrementing the major version.
• After 1.0.0 no new public API should be added without incrementing the minor version. This includes, in particular, new types, functions, methods and method overloads, from Base or other packages.

Note that Pkg.jl deviates from the SemVer specification when it comes to versions pre-1.0.0. See the section on pre-1.0 behavior for more details.

### The [deps] section

All dependencies of the package/project are listed in the [deps] section. Each dependency is listed as a name-uuid pair, for example:

[deps]
Example = "7876af07-990d-54b4-ab0e-23690620f79a"
Test = "8dfed614-e22c-5e08-85e1-65c5234f0b40"

Typically it is not needed to manually add entries to the [deps] section; this is instead handled by Pkg operations such as add.

### The [compat] section

Compatibility constraints for the dependencies listed under [deps] can be listed in the [compat] section. Example:

[deps]
Example = "7876af07-990d-54b4-ab0e-23690620f79a"

[compat]
Example = "1.2"

The Compatibility section describes the different possible compatibility constraints in detail. It is also possible to list constraints on julia itself, although julia is not listed as a dependency in the [deps] section:

[compat]
julia = "1.1"

## Manifest.toml

The manifest file is an absolute record of the state of the packages in the environment. It includes exact information about (direct and indirect) dependencies of the project. Given a Project.toml + Manifest.toml pair, it is possible to instantiate the exact same package environment, which is very useful for reproducibility. For the details, see Pkg.instantiate.

Note

The Manifest.toml file is generated and maintained by Pkg and, in general, this file should never be modified manually.

### Manifest.toml entries

Each dependency has its own section in the manifest file, and its content varies depending on how the dependency was added to the environment. Every dependency section includes a combination of the following entries:

• uuid: the UUID for the dependency, for example uuid = "7876af07-990d-54b4-ab0e-23690620f79a".
• deps: a vector listing the dependencies of the dependency, for example deps = ["Example", "JSON"].
• version: a version number, for example version = "1.2.6".
• path: a file path to the source code, for example path = /home/user/Example.
• repo-url: a URL to the repository where the source code was found, for example repo-url = "https://github.com/JuliaLang/Example.jl.git".
• repo-rev: a git revision, for example a branch repo-rev = "master" or a commit repo-rev = "66607a62a83cb07ab18c0b35c038fcd62987c9b1".
• git-tree-sha1: a content hash of the source tree, for example git-tree-sha1 = "ca3820cc4e66f473467d912c4b2b3ae5dc968444".

When a package is added from a package registry, for example by invoking pkg> add Example or with a specific version pkg> add Example@1.2, the resulting Manifest.toml entry looks like:

[[Example]]
deps = ["DependencyA", "DependencyB"]
uuid = "7876af07-990d-54b4-ab0e-23690620f79a"
version = "1.2.3"

Note, in particular, that no repo-url is present, since that information is included in the registry where this package were found.

The resulting dependency section when adding a package specified by a branch, e.g. pkg> add Example#master or pkg> add https://github.com/JuliaLang/Example.jl.git, looks like:

[[Example]]
deps = ["DependencyA", "DependencyB"]
git-tree-sha1 = "54c7a512469a38312a058ec9f429e1db1f074474"
repo-rev = "master"
repo-url = "https://github.com/JuliaLang/Example.jl.git"
uuid = "7876af07-990d-54b4-ab0e-23690620f79a"
version = "1.2.4"

Note that both the branch we are tracking (master) and the remote repository url ("https://github.com/JuliaLang/Example.jl.git") are stored in the manifest.

The resulting dependency section when adding a package specified by a commit, e.g. pkg> add Example#cf6ba6cc0be0bb5f56840188563579d67048be34, looks like:

[[Example]]
deps = ["DependencyA", "DependencyB"]
git-tree-sha1 = "54c7a512469a38312a058ec9f429e1db1f074474"
repo-rev = "cf6ba6cc0be0bb5f56840188563579d67048be34"
repo-url = "https://github.com/JuliaLang/Example.jl.git"
uuid = "7876af07-990d-54b4-ab0e-23690620f79a"
version = "1.2.4"

The only difference from tracking a branch is the content of repo-rev.

#### Developed package

The resulting dependency section when adding a package with develop, e.g. pkg> develop Example or pkg> develop /path/to/local/folder/Example, looks like:

[[Example]]
deps = ["DependencyA", "DependencyB"]
path = "/home/user/.julia/dev/Example/"
uuid = "7876af07-990d-54b4-ab0e-23690620f79a"
version = "1.2.4"

Note that the path to the source code is included, and changes made to that source tree is directly reflected.

#### Pinned package

Pinned packages are also recorded in the manifest file; the resulting dependency section for e.g. pkg> add Example; pin Example looks like:

[[Example]]
deps = ["DependencyA", "DependencyB"]
git-tree-sha1 = "54c7a512469a38312a058ec9f429e1db1f074474"
pinned = true
uuid = "7876af07-990d-54b4-ab0e-23690620f79a"
version = "1.2.4"

The only difference is the addition of the pinned = true entry.

#### Multiple package with the same name

Julia differentiates packages based on UUID, which means that the name alone is not enough to identify a package. It is possible to have multiple packages in the same environment with the same name, but with different UUID. In such a situation the Manifest.toml file looks a bit different. Consider for example the situation where you have added A and B to your environment, and the Project.toml file looks as follows:

[deps]
B = "edca9bc6-334e-11e9-3554-9595dbb4349c"

If A now depends on B = "f41f7b98-334e-11e9-1257-49272045fb24", i.e. another package named B there will be two different B packages in the Manifest.toml file. In this case the full Manifest.toml file, with git-tree-sha1 and version fields removed for clarity, looks like:

[[A]]
uuid = "edca9bc6-334e-11e9-3554-9595dbb4349c"
There is now an array of the two B packages, and the [deps] section for A has been expanded in order to be explicit about which B package A depends on.