[API reference](https://evolu.dev/docs/api-reference) › [@evolu/common](https://evolu.dev/docs/api-reference/common) › [Config](https://evolu.dev/docs/api-reference/common/Config) › EnvName

```ts
type EnvName = string &
  import("./Brand.ts").Brand<"ConstantCaseIdentifier"> &
  import("./Brand.ts").Brand<"MaxLength255">;
```

Defined in: [packages/common/src/Config.ts:76](https://github.com/evoluhq/evolu/blob/dd96d79f1dbe9a49fa12ce8e0aa7d3d0177795ca/packages/common/src/Config.ts#L76)

An environment variable name in Evolu's configuration convention.

Names are [ConstantCaseIdentifier](https://evolu.dev/docs/api-reference/common/Type/variables/ConstantCaseIdentifier)s of at most 255 characters, including
the application prefix. This is an Evolu convention, not an operating-system
limit. Double underscores do not introduce nesting.

### Example

```ts

assertOk(EnvName.fromUnknown("APP_MAX_OWNER_BYTES"), "APP_MAX_OWNER_BYTES");
assertErr(EnvName.fromUnknown("APP_maxOwnerBytes"));
assertErr(EnvName.fromUnknown("APP_DB__PORT"));
```