[Home](./index.md) > [@firebase/database](./database.md) > [Reference](./database.reference.md) > [key](./database.reference.key.md) ## Reference.key property The last part of the `Reference`'s path. For example, `"ada"` is the key for `https://.firebaseio.com/users/ada`. The key of a root `Reference` is `null`. Signature: ```typescript readonly key: string | null; ```