What happens inside a swap when the network suddenly gets congested

07 September 2026

When the network becomes congested mid-swap, the swap does not fail - it stalls. The exchanger has already broadcast the deposit transaction, but the confirmation clock stops until the backlog clears.

Here is what actually happens step by step.

The deposit transaction sits unconfirmed

The first thing a swap requires is that your deposit transaction gets at least one confirmation. Network congestion means miners or validators have more pending transactions than they can fit in the next block. They prioritize transactions offering higher fees. If your deposit transaction carries a fee that was reasonable under normal conditions, it now falls to the back of the queue.

Your transaction sits in the mempool - the waiting room for unconfirmed transactions. It stays there until either a miner includes it or it drops out entirely after a timeout (typically 24 - 72 hours, depending on the chain).

The exchanger sees nothing

From the exchanger’s perspective, your deposit address remains empty. Its automated system polls the blockchain for a confirmed transaction. It does not see your unconfirmed broadcast. The swap timer starts only after the first confirmation lands.

This is the most common reason a swap appears to hang: the user sees "broadcast" in their wallet and assumes the exchanger should act. The exchanger cannot act until the network confirms the deposit.

The confirmation finally arrives

Once your transaction confirms, the exchanger sees the deposit and proceeds. But congestion often affects the next steps too. The exchanger must broadcast its own transactions - the swap to the destination asset and the send to your address. If the network remains congested, those outgoing transactions also queue up.

The total delay compounds: deposit confirmation delay plus potential outgoing confirmation delay.

What the exchanger does (and does not do)

The exchanger does not: - Resend your transaction with a higher fee. It cannot modify a transaction it did not create. - Cancel the swap automatically. The swap remains open until the deposit confirms or the timeout expires. - Prioritize your swap over others. The system processes deposits in order of confirmation time.

The exchanger does: - Monitor the mempool for your transaction ID if its software supports that feature. - Retain the swap order for a set period (typically several hours to a day). - Process the swap normally once the deposit confirms, even if congestion has passed.

What you can do

If your deposit transaction is stuck and the swap has not timed out, your options depend on your wallet. Some wallets allow you to replace the transaction with a higher fee using Replace-by-Fee (RBF) or a child-pays-for-parent (CPFP) acceleration. This can push your transaction into the next block. The exchanger will accept the transaction regardless of which fee you paid - it only cares that the deposit arrives.

If the swap times out before your deposit confirms, the exchange order expires. The exchanger will not process it. Your transaction, once it eventually confirms, sends funds to the deposit address the exchanger controlled. You would then need to contact support to recover those funds.

For a fuller picture of what to check while a swap appears stuck, read the hub page "Why a swap sits pending and what to check". It covers the common causes that are not network congestion - wallet errors, wrong network selection, and address mismatches - which together account for more stalled swaps than congestion does.

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