> For the complete documentation index, see [llms.txt](https://error.angular-package.dev/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://error.angular-package.dev/commonerror/properties/id.md).

# #id?

## `#id?`

Optional privately stored unique [identification](/getting-started/basic-concepts.md#identification) of the described [problem](/getting-started/basic-concepts.md#problem) of generic type variable [`Id`](/commonerror/generic-type-variables.md#commonerror-less-than-id-greater-than).

{% code title="common-error.class.ts" %}

```typescript
#id?: Id;
```

{% endcode %}

### Type

#### [<mark style="color:green;">`Id`</mark>](/commonerror/generic-type-variables.md#wrap-opening)