What Block Builder Data Reveals
Block builder data directly reflects the most critical reality of the Ethereum network today: extreme concentration of power and profits. By analyzing this data, you can see who dominates transaction packaging, how they make money, and what this means for ordinary users' transactions.
Seeing "Who's in Charge" from the Data
First, block builder data clearly reveals the market landscape. Since Ethereum transitioned to PoS and adopted MEV-Boost, over 90% of Ethereum blocks are now built by dedicated builders rather than validators themselves.
And the market share of these builders is highly concentrated. According to data from 2024 to 2025, beaverbuild.org and Titan Builder together produce roughly 80% of Ethereum mainnet blocks, forming a de facto duopoly. The top three builders (including rsync-builder) hold a combined market share of over 85%. You can view real-time builder market shares via public dashboards like the MEV-Boost Dashboard, where Titan once held 44.46% and Beaverbuild 42.53%.
How They Make Money
The data also reveals builders' profit models and competitive advantages. Builders' profits are highly dependent on order flow, especially exclusive order flow.
Public vs. Private Transactions: Profits from transactions extracted from the public mempool get diluted. What truly sets builders apart is private transactions from wallets, trading bots, and other sources. Research shows that private order flow contributes 54.59% of total block value.
The Power of Exclusive Deals: A prime example is Titan Builder signing an exclusive agreement with the well-known trading bot Banana Gun in April 2023, securing all its private order flow. This move propelled its market share from less than 1% to over 40%. Its profit margin subsequently reached a staggering 17.75%, far exceeding Beaverbuild's 9%.
Real Impact on Your Transactions
This data can also explain why your transactions sometimes get "sandwiched" or experience unexpected slippage—because builders have the power to reorder transactions to maximize their own profits (i.e., MEV).
Sandwich Attacks Are Common: Research finds that sandwich attacks occur very frequently, averaging more than one per block. Attackers (searchers or builders) insert transactions before and after yours, manipulating prices to profit while you bear the slippage loss.
Quantified Impact: Data shows the immense impact of these MEV operations. To offset the effects of MEV bots on transaction ordering, network participants pay an extra average of $0.39 per transaction, totaling nearly $455,000 daily.
Tools and Risks
You can check builders' real-time market share and block counts on sites like the MEV-Boost Dashboard (mevboost.pics). When reviewing transaction details on a block explorer (e.g., Etherscan), if you see large transactions from the same address immediately before and after yours, you may have been sandwiched.
Additionally, risk alert: The high concentration in the block building market raises concerns about potential censorship capabilities. A handful of builders could theoretically refuse to include transactions from specific addresses, undermining the network's neutrality.
