Flashbots Protect

Flashbots Protect is a public service that provides a secure gateway for submitting Ethereum transactions, designed to protect users from harmful Maximal Extractable Value (MEV) strategies like frontrunning and sandwich attacks. By routing transactions through the Flashbots private mempool (also known as the SUAVE-aligned relay network), it prevents opportunistic bots on the public mempool from seeing and exploiting pending transactions for profit. This service is offered as a free RPC endpoint that any wallet or dApp can integrate, effectively creating a private channel to block builders.

The core mechanism relies on the sealed-bid auction model pioneered by Flashbots. Transactions sent via Protect are bundled and submitted directly to professional block builders, who compete to include them in the next block without revealing their contents to the general network. This process eliminates the public visibility that predatory bots rely on. Crucially, users maintain transaction privacy only until the block is proposed, at which point the transaction is executed on-chain with the same finality as a standard transaction, but with a significantly reduced risk of being exploited.

For the end-user, using Flashbots Protect is often as simple as selecting it as a network option in a supporting wallet like MetaMask. The service handles the complexities of bundle submission and auction mechanics in the background. Its primary benefits are protection from value extraction, potentially better gas estimation leading to lower overall costs (by avoiding failed frontrun attempts), and the ethical stance of not rewarding harmful MEV. It represents a practical application of MEV-aware infrastructure that shifts advantage back to regular users.

It is important to distinguish Flashbots Protect from simple transaction acceleration services. While both aim to improve transaction outcomes, Protect's fundamental goal is censorship resistance against malicious bots, not just speed. Transactions sent via Protect are also not subject to the same gas price auctions that occur in the public mempool, which can lead to more predictable fees. However, as a trade-off for privacy, transactions are only included if a builder selects the bundle, though in practice reliability is very high for standard transactions.

The development of Flashbots Protect is part of a broader ecosystem initiative to democratize access to MEV protection. It complements other Flashbots products like the Flashbots Auction for searchers and the SUAVE platform. By providing this public good, Flashbots aims to mitigate the negative externalities of MEV, making DeFi and other on-chain activities safer and more equitable for all participants without requiring them to understand the underlying complexities of blockchain mempool dynamics.

Flashbots Protect is a free, public service that functions as an alternative to the standard Ethereum public mempool. When a user submits a transaction via its RPC endpoint, it is sent directly to a network of searchers and builders within the Flashbots ecosystem, bypassing the open network where it could be frontrun or sandwiched. This private transaction flow prevents opportunistic bots from seeing the transaction details until it is included in a block, thereby neutralizing common forms of harmful MEV extraction.

The core mechanism relies on the Flashbots Auction, a two-stage process. First, specialized searchers analyze the private transaction and may bundle it with others to create profitable MEV opportunities, such as arbitrage or liquidations. These bundles are then sent to block builders, who compete to construct the most valuable block by including the most profitable bundles. Crucially, builders submit their complete block proposals directly to validators via mev-boost, ensuring the transaction is only revealed upon successful block inclusion.

For the end-user, using Flashbots Protect is as simple as selecting Flashbots Protect RPC in their wallet interface (like MetaMask) or connecting to the public endpoint https://rpc.flashbots.net. The service is non-custodial and does not require an API key. Its primary benefit is transaction privacy during the pre-confirmation phase, which protects against predatory trading strategies that exploit visible pending transactions in the public mempool.

A key feature is its commitment to failed transaction protection. When a transaction submitted via Protect fails (e.g., due to a revert or insufficient gas), it is not broadcast to the public chain, and the user is not charged any gas fees. This gasless failure model contrasts with the public mempool, where failed transactions still incur costs, providing significant economic safety for users interacting with complex DeFi protocols.

Flashbots Protect is part of a broader suite of infrastructure aimed at democratizing MEV. By providing a public good that routes transactions through a private channel, it mitigates the negative externalities of MEV for ordinary users while allowing the value extraction to be competed over in a transparent, efficient marketplace via the builder ecosystem. It represents a critical piece of infrastructure for fairer transaction ordering on Ethereum.

The journey begins when a user signs and broadcasts a transaction, typically via their wallet. In a traditional public mempool model, this transaction becomes immediately visible to all network participants, including searchers who scan for profitable MEV opportunities. This exposure creates significant risks: transactions can be front-run, where a searcher's identical but higher-fee transaction is processed first to capture a trading profit, or sandwiched, where buy and sell orders are placed around the user's trade to extract value from slippage. For users, this results in failed transactions, worse prices, and a poor experience.

Flashbots Protect, specifically its RPC endpoint (rpc.flashbots.net), provides an alternative route. Instead of broadcasting to the public Ethereum mempool, transactions are sent directly to the Flashbots relay. This relay acts as a private communication channel to block builders, who are entities that assemble the contents of a new block. By bypassing the public mempool, the transaction details are hidden from general network observers, eliminating the surface area for front-running and sandwich attacks during the propagation phase. This is the core of transaction privacy in the MEV supply chain.

Once received by the relay, the transaction is forwarded to a network of builders who compete to create the most profitable block. Builders incorporate the user's transaction into their block proposals alongside bundles from searchers. Crucially, Flashbots Protect transactions are given priority—they cannot be displaced by other transactions paying higher fees within the same builder's block. This guarantee protects against time-bandit attacks, where a searcher might try to reorganize the chain to steal a pending transaction. The builder's block is then sent to the relay, which validates it before passing it to validators (or proposers) for inclusion in the blockchain.

The final step occurs when a validator, selected to propose the next block, retrieves the most profitable block from the relay. They then attest to and publish this block on-chain. From the user's perspective, their transaction either appears successfully in the next block or fails simulated execution and reverts without ever being publicly broadcast, saving them gas fees. This end-to-end process, known as the Flashbots Protect pipeline, demonstrates how MEV infrastructure can be redesigned to offer users credible neutrality and protection, turning a potential economic negative into a service that enhances blockchain usability.