---
'@backstage/backend-common': minor
'@backstage/cli': minor
'@backstage/config-loader': minor
---

Added support for loading and validating configuration schemas, as well as declaring config visibility through schemas.

The new `loadConfigSchema` function exported by `@backstage/config-loader` allows for the collection and merging of configuration schemas from all nearby dependencies of the project.

A configuration schema is declared using the `https://backstage.io/schema/config-v1` JSON Schema meta schema, which is based on draft07. The only difference to the draft07 schema is the custom `visibility` keyword, which is used to indicate whether the given config value should be visible in the frontend or not. The possible values are `frontend`, `backend`, and `secret`, where `backend` is the default. A visibility of `secret` has the same scope at runtime, but it will be treated with more care in certain contexts, and defining both `frontend` and `secret` for the same value in two different schemas will result in an error during schema merging.

Packages that wish to contribute configuration schema should declare it in a root `"configSchema"` field in `package.json`. The field can either contain an inlined JSON schema, or a relative path to a schema file. Schema files can be in either `.json` or `.d.ts` format.

TypeScript configuration schema files should export a single `Config` type, for example:

```ts
export interface Config {
  app: {
    /**
     * Frontend root URL
     * @visibility frontend
     */
    baseUrl: string;
  };
}
```