The Manifest Format - The Cargo Book

## The Manifest Format

The `Cargo.toml` file for each package is called its manifest. It is written in the TOML format. Every manifest file consists of the following sections:

- `cargo-features` — Unstable, nightly-only features.
- `[package]` — Defines a package.
  - `name` — The name of the package.
  - `version` — The version of the package.
  - `authors` — The authors of the package.
  - `edition` — The Rust edition.
  - `rust-version` — The minimal supported Rust version.
  - `description` — A description of the package.
  - `documentation` — URL of the package documentation.
  - `readme` — Path to the package's README file.
  - `homepage` — URL of the package homepage.
  - `repository` — URL of the package source repository.
  - `license` — The package license.
  - `license-file` — Path to the text of the license.
  - `keywords` — Keywords for the package.
  - `categories` — Categories of the package.
  - `workspace` — Path to the workspace for the package.
  - `build` — Path to the package build script.
  - `links` — Name of the native library the package links with.
  - `exclude` — Files to exclude when publishing.
  - `include` — Files to include when publishing.
  - `publish` — Can be used to prevent publishing the package.
  - `metadata` — Extra settings for external tools.
  - `default-run` — The default binary to run by `cargo run`.
  - `autobins` — Disables binary auto discovery.
  - `autoexamples` — Disables example auto discovery.
  - `autotests` — Disables test auto discovery.
  - `autobenches` — Disables bench auto discovery.
  - `resolver` — Sets the dependency resolver to use.
- Target tables: (see configuration for settings)
  - `[lib]` — Library target settings.
  - `[[bin]]` — Binary target settings.
  - `[[example]]` — Example target settings.
  - `[[test]]` — Test target settings.
  - `[[bench]]` — Benchmark target settings.
- Dependency tables:
  - `[dependencies]` — Package library dependencies.
  - `[dev-dependencies]` — Dependencies for examples, tests, and benchmarks.
  - `[build-dependencies]` — Dependencies for build scripts.
  - `[target]` — Platform-specific dependencies.
- `[badges]` — Badges to display on a registry.
- `[features]` — Conditional compilation features.
- `[patch]` — Override dependencies.
- `[replace]` — Override dependencies (deprecated).
- `[profile]` — Compiler settings and optimizations.
- `[workspace]` — The workspace definition.

### The `[package]` section

The first section in a `Cargo.toml` is `[package]`.

    [package]
    name = "hello_world" # the name of the package
    version = "0.1.0"    # the current version, obeying semver
    authors = ["Alice <a@example.com>", "Bob <b@example.com>"]

The only fields required by Cargo are `name` and `version`. If publishing to a registry, the registry may require additional fields. See the notes below and the publishing chapter for requirements for publishing to crates.io.

#### The `name` field

The package name is an identifier used to refer to the package. It is used when listed as a dependency in another package, and as the default name of inferred lib and bin targets.

The name must use only alphanumeric characters or `-` or `_`, and cannot be empty. Note that `cargo new` and `cargo init` impose some additional restrictions on the package name, such as enforcing that it is a valid Rust identifier and not a keyword. crates.io imposes even more restrictions, such as enforcing only ASCII characters, not a reserved name, not a special Windows name such as "nul", is not too long, etc.

#### The `version` field

Cargo bakes in the concept of Semantic Versioning, so make sure you follow some basic rules:

- Before you reach 1.0.0, anything goes, but if you make breaking changes, increment the minor version. In Rust, breaking changes include adding fields to structs or variants to enums.
- After 1.0.0, only make breaking changes when you increment the major version. Don’t break the build.
- After 1.0.0, don’t add any new public API (no new `pub` anything) in patch-level versions. Always increment the minor version if you add any new `pub` structs, traits, fields, types, functions, methods or anything else.
- Use version numbers with three numeric parts such as 1.0.0 rather than 1.0.

See the Resolver chapter for more information on how Cargo uses versions to resolve dependencies, and for guidelines on setting your own version. See the SemVer compatibility chapter for more details on exactly what constitutes a breaking change.

#### The `authors` field

The optional `authors` field lists people or organizations that are considered the "authors" of the package. The exact meaning is open to interpretation — it may list the original or primary authors, current maintainers, or owners of the package. An optional email address may be included within angled brackets at the end of each author entry.

This field is only surfaced in package metadata and in the `CARGO_PKG_AUTHORS` environment variable within `build.rs`. It is not displayed in the crates.io user interface.

> Warning: Package manifests cannot be changed once published, so this field cannot be changed or removed in already-published versions of a package.

#### The `edition` field

The `edition` key is an optional key that affects which Rust Edition your package is compiled with. Setting the `edition` key in `[package]` will affect all targets/crates in the package, including test suites, benchmarks, binaries, examples, etc.

    [package]
    # ...
    edition = '2021'

Most manifests have the `edition` field filled in automatically by `cargo new` with the latest stable edition. By default `cargo new` creates a manifest with the 2021 edition currently.

If the `edition` field is not present in `Cargo.toml`, then the 2015 edition is assumed for backwards compatibility. Note that all manifests created with `cargo new` will not use this historical fallback because they will have `edition` explicitly specified to a newer value.

#### The `rust-version` field

The `rust-version` field is an optional key that tells cargo what version of the Rust language and compiler your package can be compiled with. If the currently selected version of the Rust compiler is older than the stated version, cargo will exit with an error, telling the user what version is required.

The first version of Cargo that supports this field was released with Rust 1.56.0. In older releases, the field will be ignored, and Cargo will display a warning.

    [package]
    # ...
    rust-version = "1.56"

The Rust version must be a bare version number with two or three components; it cannot include semver operators or pre-release identifiers. Compiler pre-release identifiers such as -nightly will be ignored while checking the Rust version. The `rust-version` must be equal to or newer than the version that first introduced the configured `edition`.

The `rust-version` may be ignored using the `--ignore-rust-version` option.

Setting the `rust-version` key in `[package]` will affect all targets/crates in the package, including test suites, benchmarks, binaries, examples, etc.

#### The `description` field

The description is a short blurb about the package. crates.io will display this with your package. This should be plain text (not Markdown).

    [package]
    # ...
    description = "A short description of my package"

> Note: crates.io requires the `description` to be set.

#### The `documentation` field

The `documentation` field specifies a URL to a website hosting the crate's documentation. If no URL is specified in the manifest file, crates.io will automatically link your crate to the corresponding docs.rs page.

    [package]
    # ...
    documentation = "https://docs.rs/bitflags"

#### The `readme` field

The `readme` field should be the path to a file in the package root (relative to this `Cargo.toml`) that contains general information about the package. This file will be transferred to the registry when you publish. crates.io will interpret it as Markdown and render it on the crate's page.

    [package]
    # ...
    readme = "README.md"

If no value is specified for this field, and a file named `README.md`, `README.txt` or `README` exists in the package root, then the name of that file will be used. You can suppress this behavior by setting this field to `false`. If the field is set to `true`, a default value of `README.md` will be assumed.

#### The `homepage` field

The `homepage` field should be a URL to a site that is the home page for your package.

    [package]
    # ...
    homepage = "https://serde.rs/"

#### The `repository` field

The `repository` field should be a URL to the source repository for your package.

    [package]
    # ...
    repository = "https://github.com/rust-lang/cargo/"

#### The `license` and `license-file` fields

The `license` field contains the name of the software license that the package is released under. The `license-file` field contains the path to a file containing the text of the license (relative to this `Cargo.toml`).

crates.io interprets the `license` field as an SPDX 2.1 license expression. The name must be a known license from the SPDX license list 3.11. Parentheses are not currently supported. See the SPDX site for more information.

SPDX license expressions support AND and OR operators to combine multiple licenses.1

    [package]
    # ...
    license = "MIT OR Apache-2.0"

Using `OR` indicates the user may choose either license. Using `AND` indicates the user must comply with both licenses simultaneously. The `WITH` operator indicates a license with a special exception. Some examples:

- `MIT OR Apache-2.0`
- `LGPL-2.1-only AND MIT AND BSD-2-Clause`
- `GPL-2.0-or-later WITH Bison-exception-2.2`

If a package is using a nonstandard license, then the `license-file` field may be specified in lieu of the `license` field.

    [package]
    # ...
    license-file = "LICENSE.txt"

> Note: crates.io requires either `license` or `license-file` to be set.

1

Previously multiple licenses could be separated with a `/`, but that usage is deprecated.

#### The `keywords` field

The `keywords` field is an array of strings that describe this package. This can help when searching for the package on a registry, and you may choose any words that would help someone find this crate.

    [package]
    # ...
    keywords = ["gamedev", "graphics"]

> Note: crates.io has a maximum of 5 keywords. Each keyword must be ASCII text, start with a letter, and only contain letters, numbers, `_` or `-`, and have at most 20 characters.

#### The `categories` field

The `categories` field is an array of strings of the categories this package belongs to.

    categories = ["command-line-utilities", "development-tools::cargo-plugins"]

> Note: crates.io has a maximum of 5 categories. Each category should match one of the strings available at https://crates.io/category_slugs, and must match exactly.

#### The `workspace` field

The `workspace` field can be used to configure the workspace that this package will be a member of. If not specified this will be inferred as the first Cargo.toml with `[workspace]` upwards in the filesystem. Setting this is useful if the member is not inside a subdirectory of the workspace root.

    [package]
    # ...
    workspace = "path/to/workspace/root"

This field cannot be specified if the manifest already has a `[workspace]` table defined. That is, a crate cannot both be a root crate in a workspace (contain `[workspace]`) and also be a member crate of another workspace (contain `package.workspace`).

For more information, see the workspaces chapter.

#### The `build` field

The `build` field specifies a file in the package root which is a build script for building native code. More information can be found in the build script guide.

    [package]
    # ...
    build = "build.rs"

The default is `"build.rs"`, which loads the script from a file named `build.rs` in the root of the package. Use `build = "custom_build_name.rs"` to specify a path to a different file or `build = false` to disable automatic detection of the build script.

#### The `links` field

The `links` field specifies the name of a native library that is being linked to. More information can be found in the `links` section of the build script guide.

    [package]
    # ...
    links = "foo"

#### The `exclude` and `include` fields

The `exclude` and `include` fields can be used to explicitly specify which files are included when packaging a project to be published, and certain kinds of change tracking (described below). The patterns specified in the `exclude` field identify a set of files that are not included, and the patterns in `include` specify files that are explicitly included. You may run `cargo package --list` to verify which files will be included in the package.

    [package]
    # ...
    exclude = ["/ci", "images/", ".*"]

    [package]
    # ...
    include = ["/src", "COPYRIGHT", "/examples", "!/examples/big_example"]

The default if neither field is specified is to include all files from the root of the package, except for the exclusions listed below.

If `include` is not specified, then the following files will be excluded:

- If the package is not in a git repository, all "hidden" files starting with a dot will be skipped.
- If the package is in a git repository, any files that are ignored by the gitignore rules of the repository and global git configuration will be skipped.

Regardless of whether `exclude` or `include` is specified, the following files are always excluded:

- Any sub-packages will be skipped (any subdirectory that contains a `Cargo.toml` file).
- A directory named `target` in the root of the package will be skipped.

The following files are always included:

- The `Cargo.toml` file of the package itself is always included, it does not need to be listed in `include`.
- A minimized `Cargo.lock` is automatically included if the package contains a binary or example target, see `cargo package` for more information.
- If a `license-file` is specified, it is always included.

The options are mutually exclusive; setting `include` will override an `exclude`. If you need to have exclusions to a set of `include` files, use the `!` operator described below.

The patterns should be gitignore-style patterns. Briefly:

- `foo` matches any file or directory with the name `foo` anywhere in the package. This is equivalent to the pattern `**/foo`.
- `/foo` matches any file or directory with the name `foo` only in the root of the package.
- `foo/` matches any directory with the name `foo` anywhere in the package.
- Common glob patterns like `*`, `?`, and `[]` are supported:
  - `*` matches zero or more characters except `/`. For example, `*.html` matches any file or directory with the `.html` extension anywhere in the package.
  - `?` matches any character except `/`. For example, `foo?` matches `food`, but not `foo`.
  - `[]` allows for matching a range of characters. For example, `[ab]` matches either `a` or `b`. `[a-z]` matches letters a through z.
- `**/` prefix matches in any directory. For example, `**/foo/bar` matches the file or directory `bar` anywhere that is directly under directory `foo`.
- `/**` suffix matches everything inside. For example, `foo/**` matches all files inside directory `foo`, including all files in subdirectories below `foo`.
- `/**/` matches zero or more directories. For example, `a/**/b` matches `a/b`, `a/x/b`, `a/x/y/b`, and so on.
- `!` prefix negates a pattern. For example, a pattern of `src/*.rs` and `!foo.rs` would match all files with the `.rs` extension inside the `src` directory, except for any file named `foo.rs`.

The include/exclude list is also used for change tracking in some situations. For targets built with `rustdoc`, it is used to determine the list of files to track to determine if the target should be rebuilt. If the package has a build script that does not emit any `rerun-if-*` directives, then the include/exclude list is used for tracking if the build script should be re-run if any of those files change.

#### The `publish` field

The `publish` field can be used to prevent a package from being published to a package registry (like crates.io) by mistake, for instance to keep a package private in a company.

    [package]
    # ...
    publish = false

The value may also be an array of strings which are registry names that are allowed to be published to.

    [package]
    # ...
    publish = ["some-registry-name"]

If publish array contains a single registry, `cargo publish` command will use it when `--registry` flag is not specified.

#### The `metadata` table

Cargo by default will warn about unused keys in `Cargo.toml` to assist in detecting typos and such. The `package.metadata` table, however, is completely ignored by Cargo and will not be warned about. This section can be used for tools which would like to store package configuration in `Cargo.toml`. For example:

    [package]
    name = "..."
    # ...

    # Metadata used when generating an Android APK, for example.
    [package.metadata.android]
    package-name = "my-awesome-android-app"
    assets = "path/to/static"

There is a similar table at the workspace level at `workspace.metadata`. While cargo does not specify a format for the content of either of these tables, it is suggested that external tools may wish to use them in a consistent fashion, such as referring to the data in `workspace.metadata` if data is missing from `package.metadata`, if that makes sense for the tool in question.

#### The `default-run` field

The `default-run` field in the `[package]` section of the manifest can be used to specify a default binary picked by `cargo run`. For example, when there is both `src/bin/a.rs` and `src/bin/b.rs`:

    [package]
    default-run = "a"

### The `[badges]` section

The `[badges]` section is for specifying status badges that can be displayed on a registry website when the package is published.

> Note: crates.io previously displayed badges next to a crate on its website, but that functionality has been removed. Packages should place badges in its README file which will be displayed on crates.io (see the `readme` field).

    [badges]
    # The `maintenance` table indicates the status of the maintenance of
    # the crate. This may be used by a registry, but is currently not
    # used by crates.io. See https://github.com/rust-lang/crates.io/issues/2437
    # and https://github.com/rust-lang/crates.io/issues/2438 for more details.
    #
    # The `status` field is required. Available options are:
    # - `actively-developed`: New features are being added and bugs are being fixed.
    # - `passively-maintained`: There are no plans for new features, but the maintainer intends to
    #   respond to issues that get filed.
    # - `as-is`: The crate is feature complete, the maintainer does not intend to continue working on
    #   it or providing support, but it works for the purposes it was designed for.
    # - `experimental`: The author wants to share it with the community but is not intending to meet
    #   anyone's particular use case.
    # - `looking-for-maintainer`: The current maintainer would like to transfer the crate to someone
    #   else.
    # - `deprecated`: The maintainer does not recommend using this crate (the description of the crate
    #   can describe why, there could be a better solution available or there could be problems with
    #   the crate that the author does not want to fix).
    # - `none`: Displays no badge on crates.io, since the maintainer has not chosen to specify
    #   their intentions, potential crate users will need to investigate on their own.
    maintenance = { status = "..." }

### Dependency sections

See the specifying dependencies page for information on the `[dependencies]`, `[dev-dependencies]`, `[build-dependencies]`, and target-specific `[target.*.dependencies]` sections.

### The `[profile.*]` sections

The `[profile]` tables provide a way to customize compiler settings such as optimizations and debug settings. See the Profiles chapter for more detail.