# Temporary Fee (/docs/protocols/uniswap-labs-hooks/volatile-pair/concepts/temporary-fee)

Learn how VolatilePair charges the backrun side a one-block temporary fee after a price move, and how its restore and capture parts work.

After a price move, the backrun side pays a temporary fee for one block. The hook sets it on the first swap of the block. Every swap on the backrun side pays it until the end of that block.

## Restore and capture
```
restore = restoreFraction × (newLeanPerm - oldLeanPerm)   if priceImpact >= restoreThreshold, else 0
capture = backrunCaptureFraction × priceImpact            if priceImpact >= backrunThreshold, else 0
temporary fee = restore + capture
```

* **Restore** adds back the amount the backrun side's permanent fee just dropped. With a restore fraction of 100% and a threshold of 0, the full drop is added back on every move. With a lower fraction or a higher threshold, a price move can lower the backrun side's starting fee for that block.
* **Capture** charges the backrun side a share of the price move. It applies only when the move is at least the backrun threshold. LPs receive this share when someone backruns a large trade.

The two thresholds are set separately. If both are 10 bp, moves below 10 bp have no temporary fee and larger moves get both parts.

## Starting fee for the block
| Side    | Starting fee                  |
| :------ | :---------------------------- |
| Leaning | Permanent fee                 |
| Backrun | Permanent fee + temporary fee |

If the price did not move since the last block open, the temporary fee is zero and ask plus bid equals the resting spread.

## Duration
The temporary fee lasts until the next block that contains a swap. That block's first swap recomputes it from the price impact since the previous block open. If the price has not moved since then, the new temporary fee is zero.

## Where to Go Next
* [Mid-Block Fees](/docs/protocols/uniswap-labs-hooks/volatile-pair/concepts/mid-block-fees)
* [VolatilePair Security](/docs/protocols/uniswap-labs-hooks/volatile-pair/security)