Backrunning in Crypto — What It Is and How It Works
Backrunning is when a bot trades immediately after someone else's transaction lands, capturing a price gap or imbalance the original transaction created.
Unlike a sandwich attack, backrunning doesn't make the victim's trade worse. It happens after the fact, and it's often the mechanism that keeps DEX prices in sync with the rest of the market.
How backrunning works
Step by step:
- A user submits a large swap on a DEX. Their swap pushes the pool price away from the broader market price (this is just normal AMM behavior — large swaps move prices).
- Right after that swap lands, a backrunner bot swaps in the opposite direction — restoring the pool's price toward the market average.
- The backrunner profits from the temporary mispricing the user left behind.
The user does not pay extra slippage — they got the price they expected, with their slippage tolerance respected. The backrunner is just trading the post-swap pool state.
Backrunning vs frontrunning vs sandwich
| Frontrun | Sandwich | Backrun | |
|---|---|---|---|
| Tx position | Before victim | Before + after | After only |
| Victim worse off? | Sometimes (race lost) | Yes (more slippage) | No |
| Captures | Same alpha | Slippage created | Mispricing left behind |
| Sentiment | Adversarial | Adversarial | Often considered neutral / beneficial |
Backrunning is often described as the "good MEV" — searchers competing to backrun keep DEX prices accurate without harming the original swapper.
The most common backrunning play: arbitrage
Backrunning is essentially arbitrage with a millisecond delay. The most common pattern:
- Big swap on Raydium pushes SOL/USDC price up by 0.5%.
- A backrunner sees that Orca and Meteora still have the old (lower) price.
- They buy SOL on Orca/Meteora and sell on Raydium — capturing the 0.5% gap.
- Result: all three pools converge on the new market price.
This is the same mechanism that drives CEX/DEX arbitrage — it's just on-chain-only.
On Solana specifically
Solana's combination of fast blocks (~400 ms) and many high-liquidity DEXs makes backrunning especially active:
- A swap on one DEX can be backrun on another DEX in the next block (~400 ms later).
- Searchers stream live pool state via APIs like Venum's
/v1/stream/pricesand/v1/stream/poolsto detect imbalances. - Bundles via Jito give backrunners atomic execution and priority.
Backrunning is one of the most accessible forms of MEV for solo builders on Solana — though competition has grown sharply.
When does backrunning become harmful?
The line is fuzzy. Two cases where backrunning feels closer to abuse:
- Backrunning oracle updates to attack a lending protocol — extracting from liquidation mispricings before they're patched.
- Backrunning in coordination with a frontrun — that's just a sandwich.
Pure post-tx arbitrage is broadly considered legitimate market activity.
Read next
- MEV Overview → — section index
- Sandwich Attack → — when frontrun + backrun is malicious
- Frontrunning → — the racing-ahead version
- Solana CEX/DEX Arbitrage → — backrunning's cousin: cross-venue
FAQ
Is backrunning illegal?
Generally no. It operates on public, permissionless infrastructure and doesn't degrade the victim's outcome. It's broadly considered legitimate trading activity.
Can I become a backrunner?
Yes — it's the most accessible MEV strategy for solo builders. You'll need streaming pool state, fast routing, and bundle submission. Venum wraps all three (/v1/stream/prices, /v1/quote, /v1/bundle); see their Build a Trading Bot guide.
Do I get paid extra if my swap is backrun?
No — the backrunner profits from market state, not from you. You get the same outcome with or without a backrunner present. (Some MEV-share schemes on Ethereum return a portion of backrun profits to the original swapper, but this is opt-in and rare.)
What's the smallest backrun-worthy opportunity?
Depends on fees and the venue, but on Solana a backrun usually needs a post-fee edge of $1–$5 minimum to clear the priority-fee + Jito-tip cost.