# No\_std = true metadata in Cargo.toml **URL:** \ **Category:** cargo\ **Created:** [January 28, 2017, 7:08pm UTC](https://internals.rust-lang.org/t/no-std-true-metadata-in-cargo-toml/4684 "2017-01-28T19:08:13Z")\ **Posts on this page:** 8\ **Page:** 1
**Author:** ![bascule](https://sea2.discourse-cdn.com/flex002/user_avatar/internals.rust-lang.org/bascule/32/3057_2.png) [@bascule](https://internals.rust-lang.org/u/bascule)\ **Post date:** [January 28, 2017, 7:08pm UTC](https://internals.rust-lang.org/t/no-std-true-metadata-in-cargo-toml/4684/1 "2017-01-28T19:08:13Z")
I think it would be useful to support a `no_std = true` flag in Cargo.toml, or a similar flag that indicates a crate has a `#![no_std]` compatible mode. I don’t think this flag needs to have any affect on the build process, or to replace e.g. having an optional `std` feature enabled by-default (perhaps it could, but consider that a non-goal for now). Instead, I think a `no_std = true` flag would be useful for the following reasons: - Visually displaying a “no\_std compatible” indication on a crate’s page on [https://crates.io](https://crates.io) - Enabling [https://crates.io](https://crates.io) search to filter by packages that support no\_std - cargo could warn if any of your dependencies do not have this flag (clearly there’d be a lot of false positives at first, but eventually it could be quite useful) Has this been suggested before? ---
**Author:** ![sfackler](https://sea2.discourse-cdn.com/flex002/user_avatar/internals.rust-lang.org/sfackler/32/9_2.png) [@sfackler](https://internals.rust-lang.org/u/sfackler)\ **Post date:** [January 28, 2017, 7:11pm UTC](https://internals.rust-lang.org/t/no-std-true-metadata-in-cargo-toml/4684/2 "2017-01-28T19:11:10Z")
I think [https://github.com/rust-lang/rfcs/pull/1133](https://github.com/rust-lang/rfcs/pull/1133) might cover something like this? ---
**Author:** ![bascule](https://sea2.discourse-cdn.com/flex002/user_avatar/internals.rust-lang.org/bascule/32/3057_2.png) [@bascule](https://internals.rust-lang.org/u/bascule)\ **Post date:** [January 28, 2017, 7:12pm UTC](https://internals.rust-lang.org/t/no-std-true-metadata-in-cargo-toml/4684/3 "2017-01-28T19:12:51Z")
Nice! That looks promising ---
**Author:** ![newpavlov](https://sea2.discourse-cdn.com/flex002/user_avatar/internals.rust-lang.org/newpavlov/32/3290_2.png) [@newpavlov](https://internals.rust-lang.org/u/newpavlov)\ **Post date:** [January 29, 2017, 4:15am UTC](https://internals.rust-lang.org/t/no-std-true-metadata-in-cargo-toml/4684/4 "2017-01-29T04:15:56Z")
I’ve proposed a bit more general concept [here](https://users.rust-lang.org/t/target-os-architecture-environment-as-a-crate-property/7748). Hope something similar will be included into this [RFC](https://github.com/rust-lang/rfcs/pull/1868). ---
**Author:** ![bluss](https://sea2.discourse-cdn.com/flex002/user_avatar/internals.rust-lang.org/bluss/32/2264_2.png) [@bluss](https://internals.rust-lang.org/u/bluss)\ **Post date:** [January 29, 2017, 2:29pm UTC](https://internals.rust-lang.org/t/no-std-true-metadata-in-cargo-toml/4684/5 "2017-01-29T14:29:02Z")
In the meantime, we can encourage the keyword [`no_std`](https://crates.io/keywords/no_std) for such crates. ---
**Author:** ![bascule](https://sea2.discourse-cdn.com/flex002/user_avatar/internals.rust-lang.org/bascule/32/3057_2.png) [@bascule](https://internals.rust-lang.org/u/bascule)\ **Post date:** [February 7, 2017, 9:47am UTC](https://internals.rust-lang.org/t/no-std-true-metadata-in-cargo-toml/4684/6 "2017-02-07T09:47:47Z")
Support for categorizing crates in [https://crates.io](https://crates.io) was added shortly after I asked this question. I figured it might be worth adding a category to allow easy browsing of `#![no_std]` crates: > ---
**Author:** ![bluss](https://sea2.discourse-cdn.com/flex002/user_avatar/internals.rust-lang.org/bluss/32/2264_2.png) [@bluss](https://internals.rust-lang.org/u/bluss)\ **Post date:** [February 10, 2017, 11:16pm UTC](https://internals.rust-lang.org/t/no-std-true-metadata-in-cargo-toml/4684/7 "2017-02-10T23:16:38Z")
[First is either](https://crates.io/categories/no-std) 😉[thanks to @mglagla](https://github.com/bluss/either/pull/10) ---
**Author:** ![system](https://sea2.discourse-cdn.com/flex002/user_avatar/internals.rust-lang.org/system/32/14092_2.png) [@system](https://internals.rust-lang.org/u/system)\ **Post date:** [March 25, 2019, 8:27am UTC](https://internals.rust-lang.org/t/no-std-true-metadata-in-cargo-toml/4684/8 "2019-03-25T08:27:48Z")
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