Notice to Protect users: Planned changes to ""

We are upgrading Flashbots Protect to make “fast” mode, faster. If you currently use “”, read on for more information about how your experience may change before October 11, 2023. If you don’t use fast mode, learn why it might make sense to switch.

You can opt in or out of fast mode at any time.

At a glance

After October 11, requests sent to will:

  1. Be shared with all registered builders
  2. Receive 50% of MEV-Share refunds

These changes will make Protect requests a lot faster.

  • Sharing with more builders reduces the amount of time that users have to wait for their transactions to be confirmed. Instead of waiting for the Flashbots builder to land a block, transactions can be landed by any registered builder.
  • Reducing the % of refunds shared with users increases the fees paid to validators. This makes it more likely that the user’s transactions will be included in a block.

The default RPC will remain unchanged. If you do not want to use fast mode, set your rpc to “”.

More details

History of fast mode

In March 2022, Flashbots introduced a new version of the Protect RPC that allowed transactions to revert, in exchange for quicker inclusion by miners running MEV-Geth. In September 2022, Ethereum completed the Merge, and MEV-Geth and fast mode were no longer active. Today, Protect requests that use are treated identically to the default

Builder sharing

Over the past year, a large and competitive network of block builders has emerged to produce blocks on Ethereum. While competition is good for the network, it results in slower inclusion rates for Protect users. Because users only share their transactions with the Flashbots Builder, they can only be included in a small fraction of blocks.

In July 2023, Flashbots introduced a mechanism for users to share their transactions with other builders. Users that opt in to builder sharing have much faster inclusion rates because they no longer have to wait for the Flashbots builder to land a block.


In April 2023, Flashbots introduced MEV-Share – a protocol which refunds users for the MEV that they generate. Part of this MEV is shared with the user, and the remainder is shared with the validator.

New meanings of fast

So — what does fast mean today? It’s now clear that the best way to get users’ transactions included quickly is to:

  1. Share with the most builders
  2. Pay the most fees

We’re upgrading fast mode to do both of these things. We expect that will once again be the best, fastest way to transact privately on Ethereum.

Estimated impact

Only ~0.2% of Protect users currently use the /fast option, so we expect this change to disrupt very few workflows. But we’re issuing the advance notice out of an abundance of caution.

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