# is

> **is**(`input`): `input is PieceCID`

Defined in: [packages/synapse-core/src/piece/parse.ts:65](https://github.com/FilOzone/synapse-sdk/blob/e6b9edfa98a2f726e470425e05558279dfe64dfb/packages/synapse-core/src/piece/parse.ts#L65)

Type guard for [PieceCID](/reference/filoz/synapse-core/piece/classes/piececid/) instances. Plain CIDs need [tryFrom](/reference/filoz/synapse-core/piece/functions/tryfrom/)
to gain accessors. Cross-realm/bundle safe via PIECE\_CID\_TAG.

## Parameters

| Parameter | Type |
| ------ | ------ |
| `input` | `unknown` |

## Returns

`input is PieceCID`