> For the complete documentation index, see [llms.txt](https://docs.midpointapi.com/midpoint-documentation/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://docs.midpointapi.com/midpoint-documentation/core-concepts/requests/request-id.md).

# Request ID

The Request ID is a unique on-chain and off-chain identifier genrated at runtime for a request. 

On-chain, Midpoint maintains the uniqueness of this rolling ID by incrementing the on-chain Request ID for each request. This Request ID is returned to the contract that initiated the midpoint request. This is done inside [Startpoints](/midpoint-documentation/more-reading/startpoints.md), and each chain generates a Request ID that is unique to its chain.

Off-chain, Midpoint assigns a unique rolling ID for each request that is generated. 

Request IDs allow serialization of requests as they move off-chain and then back on-chain. By posting the request ID back on-chain, you can tie a response to a particular request.