---
id: fast-foundation.key
title: Key type
hide_title: true
---
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[@microsoft/fast-foundation](./fast-foundation.md) &gt; [Key](./fast-foundation.key.md)

## Key type

A key that is used to register dependencies with a dependency injection container.

<b>Signature:</b>

```typescript
export declare type Key = PropertyKey | object | InterfaceSymbol | Constructable | Resolver;
```