# Ethereum MEV-Boost API > Who actually builds Ethereum's blocks and which relays deliver them — live from the public MEV-Boost relay APIs, no key. Since the Merge most Ethereum validators outsource block construction through MEV-Boost: specialised block builders compete to assemble the most valuable block (capturing MEV — arbitrage, liquidations, sandwiches — plus priority fees), relays act as trusted middlemen between builders and validators, and the validator simply signs the highest-paying block. This builder-and-relay market is one of the most important and most centralised pieces of Ethereum's infrastructure — a handful of builders win the large majority of blocks — so tracking who is winning and how much they pay is core to Ethereum decentralisation and MEV analytics. The builders endpoint ranks block builders by how many of the recent blocks they won, with each builder's block share, the total and average value (in ETH) they paid validators, and a name where the builder's public key is known. The relays endpoint shows each MEV-Boost relay's reach across the major relays (Flashbots, Ultrasound, bloXroute, Agnostic, Aestus, Titan). The blocks endpoint lists the most recent blocks delivered through MEV-Boost, each with its builder, the value paid to the proposer, gas used, transaction count and which relays delivered it. This is the block-building / MEV-Boost cut, the supply side of Ethereum block production — distinct from the blob-space fee market, the execution-gas oracle, the ETH supply/burn feed and the on-chain and DeFi feeds. Values are in ETH; everything is live. Built for Ethereum infrastructure, MEV research, staking and analytics tools. ## Authentication All requests require your oanor API key in the `x-oanor-key` header. Get one at https://www.oanor.com/developer/keys. ```bash curl -H "x-oanor-key: oanor_live_…" "https://api.oanor.com/mevboost-api/..." ``` ## Pricing - **Free** (Free) — 1,020 calls/Mo, 2 req/s - **Starter** ($12/Mo) — 21,800 calls/Mo, 6 req/s - **Pro** ($36/Mo) — 116,000 calls/Mo, 16 req/s - **Mega** ($79/Mo) — 642,000 calls/Mo, 40 req/s ## Endpoints ### Builders #### `GET /v1/builders` — Block builders ranked by recent blocks won **Example:** ```bash curl -H "x-oanor-key: $KEY" \ "https://api.oanor.com/mevboost-api/v1/builders" ``` **Response:** ```json { "data": { "note": "Ethereum block builders ranked by how many of the most recent MEV-Boost blocks they won, with each builder's block share, and the total and average value (ETH) they paid validators. A handful of builders win the large majority of blocks — the centralisation of block production. Names are best-effort for well-known public keys; unknown builders are shown by key. Live, cached ~60s.", "source": "Public MEV-Boost relay data APIs (proposer_payload_delivered), keyless", "builders": [ { "name": null, "blocks": 84, "pubkey_short": "0x8db2a99d…82be26", "avg_value_eth": 0.01127, "builder_pubkey": "0x8db2a99d06eb076ab83049c2dfed5725ed5cf35772071f43365399ad32e505f0e3ff1e14b9686cd74562dc50c282be26", "block_share_pct": 19.9, "total_value_eth": 0.947 }, { "name": null, "blocks": 40, "pubkey_short": "0xb26f9666…48e681", "avg_value_eth": 0.01096, "builder_pubkey": "0xb26f96664274e15fb6fcda862302e47de7e0e2a6687f8349327a9846043e42596ec44af676126e2cacbdd181f548e681", "block_share_pct": 9.5, "total_value_eth": 0.4385 }, { "name": "Titan Builder", "blocks": 39, "pubkey_short": "0x88510a78…800d65", "a …(truncated, see openapi.json for full schema) ``` ### Relays #### `GET /v1/relays` — Each MEV-Boost relay's reach **Example:** ```bash curl -H "x-oanor-key: $KEY" \ "https://api.oanor.com/mevboost-api/v1/relays" ``` **Response:** ```json { "data": { "note": "Each major MEV-Boost relay's reach over the most recent window of blocks — how many of them it delivered to validators (reach_pct = share of the window it covered). Shares overlap and sum above 100% because the same winning block is usually delivered by several relays at once, so this is reach/coverage, not an exclusive market split. live=false means the relay did not respond this cycle. Relays sampled: Flashbots, Ultrasound, bloXroute, Agnostic, Aestus, Titan. Live, cached ~60s.", "relays": [ { "live": true, "relay": "ultrasound", "reach_pct": 67, "blocks_delivered": 67 }, { "live": true, "relay": "titan", "reach_pct": 44, "blocks_delivered": 44 }, { "live": true, "relay": "bloxroute", "reach_pct": 34, "blocks_delivered": 34 }, { "live": true, "relay": "aestus", "reach_pct": 14, "blocks_delivered": 14 }, { "live": true, "relay": "flashbots", "reach_pct": 9, "blocks_delivered": 9 }, { "live": true, "relay": "agnostic", "reach_pct": 5, …(truncated, see openapi.json for full schema) ``` ### Blocks #### `GET /v1/blocks` — Most recent MEV-Boost blocks with builder and value **Parameters:** - `limit` (query, optional, string) — Number of blocks (1-100) Example: `20` **Example:** ```bash curl -H "x-oanor-key: $KEY" \ "https://api.oanor.com/mevboost-api/v1/blocks?limit=20" ``` **Response:** ```json { "data": { "note": "The most recent Ethereum blocks delivered through MEV-Boost, newest first — each with its builder, the value in ETH paid to the validator (the proposer), gas used, transaction count and which relays delivered it. Pass limit (1-100, default 20). Live, cached ~60s.", "count": 20, "blocks": [ { "slot": 14539078, "num_tx": 250, "relays": [ "ultrasound", "aestus", "titan" ], "gas_used": 30125237, "gas_limit": 60000000, "value_eth": 0.0049, "block_number": 25303514, "builder_name": null, "builder_short": "0x823e0146…80b8df", "builder_pubkey": "0x823e0146b1a5bfc5d4391f7f4391b4f170693369a2350c676238fb1bef4b2dc99bb99307f77e084920cdc7721c80b8df" }, { "slot": 14539077, "num_tx": 175, "relays": [ "ultrasound" ], "gas_used": 34009892, "gas_limit": 59999886, "value_eth": 0.00767, "block_number": 25303513, "builder_name": null, "builder_short": "0x88857150…70f93f", "builder_pubkey": "0x88857150299287cedfbadea1ee3fb7ac121f1e4e16bef44b4a7bad35432973c4009efb90394facca3fdc0759ba70f …(truncated, see openapi.json for full schema) ``` ### Meta #### `GET /v1/meta` — Service metadata **Example:** ```bash curl -H "x-oanor-key: $KEY" \ "https://api.oanor.com/mevboost-api/v1/meta" ``` **Response:** ```json { "data": { "note": "builders ranks block builders by recent blocks won; relays shows each relay's reach; blocks lists recent MEV-Boost blocks (limit 1-100). meta takes no parameters. Values are in ETH. Builder names are best-effort labels for well-known public keys; unknown builders show by key. Relay shares overlap (a block is usually delivered by several relays). A short ~60-second protective cache fronts the relay upstreams.", "source": "Public MEV-Boost relay data APIs (Flashbots, Ultrasound, bloXroute, Agnostic, Aestus, Titan), keyless, live", "service": "mevboost-api", "endpoints": { "GET /v1/meta": "This document.", "GET /v1/blocks": "Most recent MEV-Boost blocks with builder and value (limit 1-100).", "GET /v1/relays": "Each MEV-Boost relay's reach (blocks delivered).", "GET /v1/builders": "Block builders ranked by recent blocks won, with share and value paid." }, "description": "Ethereum MEV-Boost — who builds Ethereum's blocks and which relays deliver them, live from the public MEV-Boost relay APIs (no key). Since the Merge most validators outsource block construction: builders compete to assemble the most valuable block (MEV + fees), relays deliver them, the validator signs the highest bid. It exposes the block-builder market (who wins blocks, their share and the ETH they pay), each relay's reach across the major relays, and the most recent MEV-Boost blocks with t …(truncated, see openapi.json for full schema) ``` --- Marketplace page: https://www.oanor.com/api/mevboost-api OpenAPI spec: https://www.oanor.com/api/mevboost-api/openapi.json