Supported Networks

Chainlink VRF allows you to integrate provably fair and verifiably random data in your smart contract.

For implementation details, read Introduction to Chainlink VRF v2 Direct funding method.

Wrapper Parameters

These parameters are configured in the VRF v2 Wrapper contract. You can view these values by running getConfig on the VRF v2 Wrapper or by viewing the VRF v2 Wrapper contract in a blockchain explorer.

• uint32 stalenessSeconds: How long the VRF v2 Wrapper waits until we consider the ETH/LINK price used for converting gas costs to LINK is stale and use fallbackWeiPerUnitLink.
• uint32 wrapperGasOverhead: The gas overhead of the VRF v2 Wrapper’s fulfillRandomWords function.
• uint32 coordinatorGasOverhead: The gas overhead of the coordinator’s fulfillRandomWords function.
• uint8 maxNumWords: Maximum number of words that can be requested in a single wrapped VRF request.

Coordinator Parameters

Some parameters are important to know and are configured in the coordinator contract. You can view these values by running getConfig on the coordinator or by viewing the coordinator contract in a blockchain explorer.

• uint16 minimumRequestConfirmations: The minimum number of confirmation blocks on VRF requests before oracles respond
• uint32 maxGasLimit: The maximum gas limit supported for a fulfillRandomWords callback. Note that you still need to substract the wrapperGasOverhead for the accurate limit, as explained in Direct funding limits.

Fee Parameters

Fee parameters are configured in the VRF v2 Wrapper and the VRF v2 Coordinator contracts and specify the premium you pay per request in addition to the gas cost for the transaction. You can view them by running getConfig on the VRF v2 Wrapper:

• The uint32 fulfillmentFlatFeeLinkPPM parameter is a flat fee and defines the fees per request specified in millionths of LINK.
• The uint8 wrapperPremiumPercentage parameter defines the premium ratio in percentage. For example, a value of 0 indicates no premium. A value of 15 indicates a 15% premium.

The details for calculating the total transaction cost can be found here.

Configurations

VRF v2 coordinators for direct funding are available on several networks. To see a list of coordinators for subscription funding, see the Subscription Configurations page.