Flashbots & Proposer-Builder Separation
MEV extraction was chaotic — bots spammed the mempool with gas wars, congesting the network. Flashbots introduced a private channel for MEV, and PBS separated block building from block proposing. This changed Ethereum's entire transaction supply chain.
The MEV Supply Chain (Post-PBS)
Click each stage to learn more. Transactions flow from users → searchers → builders → proposers.
User
→
Mempool
→
Searcher
→
Builder
→
Relay
→
Proposer
👤 User Submits Transaction
A user signs a transaction (e.g., a Uniswap swap) and broadcasts it. Without Flashbots Protect, this goes to the public mempool where anyone can see it. With Flashbots Protect, it goes directly to builders via a private channel.
Block Building Auction Simulator
Builders compete to construct the most valuable block. The proposer picks the highest bid. Adjust MEV opportunity to see how builder competition plays out.
Winning Bid
2.13 ETH
Proposer Revenue
2.13 ETH
Builder Profit
0.37 ETH
MEV to Proposer %
85%
Public Mempool vs Flashbots Protect
Compare what happens to your transaction with and without MEV protection.
❌ Public Mempool
Transaction visible to everyone
Searchers scan for MEV opportunities
Sandwich attack extracts $5-50 per swap
Failed txs still cost gas
No privacy — all pending txs are public
✅ Flashbots Protect
Transaction sent privately to builders
Not visible in public mempool
No sandwich attacks possible
Failed txs don't cost gas (no on-chain)
Optional: get MEV refunds via MEV-Share
MEV-Share: Users Get Paid Back
MEV-Share lets users capture a portion of the MEV their transactions create. Adjust the refund rate to see the economics.
Your Refund
$13.50
Searcher Keeps
$1.50
Net Cost to You
$1.50