# ConfirmedBlockHeightExists

> Assertion whether a specified block number is confirmed.

> For the complete documentation index, see [llms.txt](/llms.txt). Markdown versions of documentation pages are available by appending `.md` to the page URL.

Source: https://dev.flare.network/fdc/attestation-types/confirmed-block-height-exists

Assertion whether a block with the specified `blockNumber` is **confirmed** with additional data to compute the **block production rate** within a given time window.

## Supported chains[​](#supported-chains "Direct link to Supported chains")

Network Type

Supported Chains

**Mainnet**

`BTC` (Bitcoin), `DOGE` (Dogecoin), `XRP` (XRP Ledger)

**Testnet**

`testBTC` (Bitcoin Testnet v3), `testDOGE`, `testXRP`

## Request[​](#request "Direct link to Request")

Field

Solidity Type

Description

`blockNumber`

`uint64`

The block number to confirm.

`queryWindow`

`uint64`

The time period (in seconds) to calculate the block production rate.

## Response[​](#response "Direct link to Response")

Field

Solidity Type

Description

`blockTimestamp`

`uint64`

The timestamp of the block at `blockNumber`.

`numberOfConfirmations`

`uint64`

The required number of confirmations for the block to be considered confirmed (chain-specific).

`lowestQueryWindowBlockNumber`

`uint64`

The block number of the latest block with a timestamp strictly less than `blockTimestamp - queryWindow`.

`lowestQueryWindowBlockTimestamp`

`uint64`

The timestamp of the block at `lowestQueryWindowBlockNumber`.

## Verification process[​](#verification-process "Direct link to Verification process")

1.  The function checks if the block with `blockNumber` is confirmed by at least the required `numberOfConfirmations` for the specified chain.
    -   If the block does not meet this requirement, the request is rejected.
    -   A block at the tip of the chain has exactly **1 confirmation**.
2.  The lowestQueryWindowBlock\` is identified, and its block number and timestamp are extracted.
3.  The required confirmations are defined based on chain-specific [finality](#finality).
4.  The returned `timestamp` is:
    -   `mediantime` for Bitcoin and Dogecoin.
    -   `close_time` for XRPL.

Lowest used timestamp

For the `lowestUsedTimestamp` parameter, the value of `lowestQueryWindowBlockTimestamp` is used.

## Finality[​](#finality "Direct link to Finality")

Blockchains have varying confirmation depths to consider blocks as final.

Chain

`chainId`

Confirmations required

Confirmation time

Bitcoin

0

6

≈60 mins

Dogecoin

2

60

≈60 mins

XRPL

3

3

≈12 seconds

## Contract Interface[​](#contract-interface "Direct link to Contract Interface")

For the complete interface definition, see [`IConfirmedBlockHeightExists`](/fdc/reference/IConfirmedBlockHeightExists).