Flashbots is a research and development project whose Protect service can route a signed Ethereum swap privately, provided your wallet uses that route without also broadcasting the transaction publicly. The swap still executes and pays gas under Ethereum’s rules; the main difference is who sees it before inclusion, with possible MEV value returned to you.
- Private submission reduces public exposure while a swap is pending.
- The wallet or application must use the selected route; signing alone does not choose one.
- Both routes follow Ethereum’s execution rules but reach block builders differently.
Private Delivery Limits Public Exposure Before Inclusion
Private delivery keeps a pending swap out of Ethereum’s public transaction pool before inclusion. Public submission propagates it across the peer-to-peer network, where observers can read its token pair, amount and slippage limit. That gives a searcher room to react, including with a sandwich: trading before and after your swap to profit from the price movement. Maximal extractable value, or MEV, is value gained through control of transaction ordering.
Protect forwards the transaction to participating block builders. That routing difference is why, when considering Flashbots, you should verify that your wallet submits through the Flashbots Protect RPC. Private means restricted distribution before inclusion, not secrecy from every intermediary. Receiving builders can see the transaction, while information shared with searchers, such as selected swap details, can widen that circle.
Your Wallet or Application Chooses the Submission Route
Your wallet or application chooses the route when it broadcasts the signed transaction. Imagine signing the same illustrative swap with the same nonce, gas settings and slippage limit. Send it to a public RPC endpoint and its provider can propagate it through the public pool. Send it through Protect and it enters the private path toward participating builders. The signature has not changed; the destination for the signed bytes has.
A wallet’s network setting may govern its own broadcasts, while a swap application may send through separate infrastructure. Identify which component calls the submission endpoint. If the transaction reaches both a private service and the public network, the public copy removes the visibility benefit, even if a builder also receives the private copy.
Ethereum Execution and Gas Rules Still Apply
Once included, either version of that swap is an ordinary Ethereum transaction. Its contract calls run against the state at its position in the block. The base fee, priority fee, gas limit and account balance requirements still apply, and the included transaction becomes public. Private delivery cannot guarantee your slippage limit will be met; earlier trades or market changes can still make execution fail.
Protect filters transactions predicted to revert before they enter a block. That can spare gas on a failed swap left out of the chain, but it does not turn a revert into a successful trade or rewrite Ethereum’s fee rules. A public transaction that reverts after inclusion consumes gas; a transaction left out of a block incurs no on-chain gas fee on either route. The Flashbots MEV-Share Node may return value when a private transaction creates an eligible backrun opportunity, such as a trade placed immediately after yours. Refunds are conditional, so budget for gas without assuming one.
Inclusion Timing Depends on Which Builders Receive the Swap
The builders that receive a swap affect its opportunities for inclusion. Public propagation makes it available to builders monitoring the public pool. Private submission depends on the service accepting it, forwarding it to selected builders, and one of those builders producing a block that includes it. Wider private distribution can improve reach but gives more parties access before inclusion; narrower distribution limits that access but may reduce chances to land. Flashbots cannot promise that every participating builder will include a pending swap.
Neither route has a universal speed advantage. A public swap may land in the next block while a private one waits for an eligible builder; the reverse can happen too. Compare builder coverage and pending-transaction handling alongside the fee you are willing to pay. A private service can stop forwarding a transaction, so understand its replacement and cancellation process rather than assuming public mempool behavior.
Privacy Depends on Service Trust and Later Rebroadcasts
Private delivery depends on the receiving service, participating builders and whether your wallet later broadcasts publicly. Those intermediaries can inspect transaction details before the public can. Changing RPC settings or resending a stuck transaction publicly can reveal the same swap while it is pending. Once observers have seen those details, switching back to private delivery cannot make them secret again. For an ordinary swap, choose private submission when limiting exposure before inclusion matters and your wallet can maintain the route; otherwise, weigh public propagation against your acceptable MEV risk.