Block Builder Submissions

External builders can submit blocks to the Blocknative Mainnet relay with support for both JSON and SSZ encoding methods, and gzip (gunzip) compression. To improve builder-to-relay latency we recommend using SSZ. The table below outlines Builder API methods available.

Relay Block Submission Endpoints

GET Request - Returns an array of validator registrations with assigned duties in the current and next epoch
POST Request - submits a block to the relay


Block submissions are currently rate-limited to 10 blocks/second per public key. A single payload has a size limit of 10MB.

Content Options

To send payloads in JSON or SSZ attach Content-Type header with either application/json or application/octet-stream respectively.
Gunzipped payloads need to have Content-Encoding header set to gzip.


If you have any questions about submitting blocks to the Blocknative relay, please join our discord.