All terms
Acting on knowledge of a pending transaction before it executes.
Because pending transactions are public, bots can see a large order coming and position ahead of it. This is illegal in traditional markets and structurally unavoidable in a public mempool.
Mitigations exist: private relays, batch auctions, encrypted mempools and order flow auctions all reduce the exposure.
CoW Swap batches orders and settles them together specifically to remove this attack surface.
That front running requires inside information. On a public blockchain the pending transaction queue is visible to everyone, so a bot can see your trade before it executes and act on it. The information is not stolen, it is published by design.
Common questions
Is front running illegal in crypto?
How is it different from a sandwich attack?
Where this comes up on the site
The guides that actually use this word, rather than a list of everything we have written.
Where to go next
More security terms
Want this explained out loud?
Some of these land faster in conversation than in writing. Sessions are one to one and you can ask anything, including the things that feel too obvious to ask.