Using Access Context Manager, you can create access levels that permit access
to data based on the context of a request. While Access Context Manager
already provides a method of creating
[basic access levels](https://docs.cloud.google.com/access-context-manager/docs/create-basic-access-level.md.txt), you can also create custom
access levels. Custom access levels enable your organization to use the device
and context data of third-party security and endpoint management vendors to
permit access to Google Cloud resources.

Custom access levels use boolean expressions written in a subset of
[Common Expression Language](https://opensource.google.com/projects/cel) (CEL)
to test the attributes of a client making a request.

In the Google Cloud console, custom access levels are configured using
**Advanced Mode** when you create an access level.

To learn more about building CEL expressions for custom access levels, see the
[custom access level specification](https://docs.cloud.google.com/access-context-manager/docs/custom-access-level-spec.md.txt).

To start using custom access levels, see
[Creating custom access levels](https://docs.cloud.google.com/access-context-manager/docs/create-custom-access-level.md.txt).

After custom access levels are created, they can be
[managed like other access levels](https://docs.cloud.google.com/access-context-manager/docs/manage-access-levels.md.txt).