#policy #authorization #oso #access-control #applications #language #rbac


Polar core library for oso, an open source policy engine for authorization that’s embedded in your application

45 releases

0.27.3 Jan 13, 2024
0.27.2 Dec 20, 2023
0.27.0 Apr 3, 2023
0.26.4 Dec 5, 2022
0.8.2 Nov 25, 2020

#316 in Development tools

Download history 4855/week @ 2024-01-31 3547/week @ 2024-02-07 3647/week @ 2024-02-14 3137/week @ 2024-02-21 3859/week @ 2024-02-28 3912/week @ 2024-03-06 3850/week @ 2024-03-13 3345/week @ 2024-03-20 3549/week @ 2024-03-27 5058/week @ 2024-04-03 3880/week @ 2024-04-10 3774/week @ 2024-04-17 3892/week @ 2024-04-24 3513/week @ 2024-05-01 4335/week @ 2024-05-08 3422/week @ 2024-05-15

15,799 downloads per month
Used in 3 crates (via oso)


17K SLoC


We have deprecated the legacy Oso open source library. We have plans for the next open source release and we’re looking forward to getting feedback from the community leading up to that point (please reach out to us in the Slack #help channel). In the meantime, if you’re happy using the Oso open source library now, nothing needs to change – i.e., we are not end-of-lifing (EOL) the library and we’ll continue to provide support and critical bug fixes. More context: here.


Development GitHub release (latest SemVer) Go version Maven version NPM version PyPI version RubyGems version Crates.io version Slack

What is Oso?

Oso is a batteries-included framework for building authorization in your application.

With Oso, you can:

  • Model: Set up common permissions patterns like role-based access control (RBAC) and relationships using Oso’s built-in primitives. Extend them however you need with Oso’s declarative policy language, Polar.
  • Filter: Go beyond yes/no authorization questions. Implement authorization over collections too - e.g., “Show me only the records that Juno can see.”
  • Test: Write unit tests over your authorization logic now that you have a single interface for it. Use the Oso debugger or REPL to track down unexpected behavior.

Oso offers libraries for Node.js, Python, Go, Rust, Ruby, and Java.

Our latest creation Oso Cloud makes authorization across services as easy as oso.authorize(user, action, resource). Learn about it.


Community & Support

If you have any questions on Oso or authorization more generally, you can join our engineering team & hundreds of other developers using Oso in our community Slack:


Share your story

We'd love to hear about your use case and experience with Oso. Share your story in our Success Stories issue.



Oso's Rust core is developed against Rust's latest stable release.

Language libraries

Oso's language libraries can be developed without touching the Rust core, but you will still need the Rust stable toolchain installed in order to build the core.

To build the WebAssembly core for the Node.js library, you will need to have wasm-pack installed and available on your system PATH.

Language requirements

To work on a language library, you will need to meet the following version requirements:

  • Java: 11+
    • Maven: 3.6+
  • Node.js: 12.20.0+
    • Yarn 1.22+
  • Python: 3.7+
  • Ruby: 2.4+
    • Bundler 2.1.4+
  • Rust: 1.46+
  • Go: 1.14+

Contributing & Jobs


If you want to work on the Oso codebase full-time, visit our jobs page.




~69K SLoC