# findPieceIdsByCid

> **findPieceIdsByCid**(`client`, `options`): [`Promise`](https://developer.mozilla.org/docs/Web/JavaScript/Reference/Global_Objects/Promise)\<[`OutputType`](/reference/filoz/synapse-core/pdp-verifier/namespaces/findpieceidsbycid/type-aliases/outputtype/)\>

Defined in: [packages/synapse-core/src/pdp-verifier/find-piece-ids-by-cid.ts:76](https://github.com/FilOzone/synapse-sdk/blob/dedad9df2a2b92b4d129e93660ac1208ef65c2c1/packages/synapse-core/src/pdp-verifier/find-piece-ids-by-cid.ts#L76)

Find piece IDs for a given PieceCID in a data set.

Uses the on-chain `findPieceIdsByCid` function for efficient CID→ID lookup.

## Parameters

| Parameter | Type | Description |
| ------ | ------ | ------ |
| `client` | `Client`\<`Transport`, `Chain`\> | The client to use to find piece IDs. |
| `options` | [`OptionsType`](/reference/filoz/synapse-core/pdp-verifier/namespaces/findpieceidsbycid/type-aliases/optionstype/) | [findPieceIdsByCid.OptionsType](/reference/filoz/synapse-core/pdp-verifier/namespaces/findpieceidsbycid/type-aliases/optionstype/) |

## Returns

[`Promise`](https://developer.mozilla.org/docs/Web/JavaScript/Reference/Global_Objects/Promise)\<[`OutputType`](/reference/filoz/synapse-core/pdp-verifier/namespaces/findpieceidsbycid/type-aliases/outputtype/)\>

Array of piece IDs matching the CID [findPieceIdsByCid.OutputType](/reference/filoz/synapse-core/pdp-verifier/namespaces/findpieceidsbycid/type-aliases/outputtype/)

## Example

```ts
import { findPieceIdsByCid } from '@filoz/synapse-core/pdp-verifier'
import { calibration } from '@filoz/synapse-core/chains'
import { createPublicClient, http } from 'viem'
import * as Piece from '@filoz/synapse-core/piece'

const client = createPublicClient({
  chain: calibration,
  transport: http(),
})

const pieceCid = Piece.parse('bafkzcibcd4bdomn3tgwgrh3g532zopskstnbrd2n3sxfqbze7rxt7vqn7veigmy')
const pieceIds = await findPieceIdsByCid(client, {
  dataSetId: 1n,
  pieceCid,
})
// pieceIds is an array of bigint IDs matching the CID
```

## Throws

Errors [findPieceIdsByCid.ErrorType](/reference/filoz/synapse-core/pdp-verifier/namespaces/findpieceidsbycid/type-aliases/errortype/)