Bitcoin Fee Strategy in SSP

Every Bitcoin transaction you send from SSP carries a fee, and that fee is not a fixed price set by SSP or by anyone else. It is a bid in an open auction. Understanding how that auction works is the difference between a transaction that confirms in ten minutes and one that sits unconfirmed for two days. This guide explains Bitcoin transaction fees in practical terms — what the unit means, why the price swings, and how to choose a sensible fee when you spend Bitcoin from your SSP 2-of-2 multisig wallet.

If you are new to how Bitcoin behaves inside SSP, start with the hub article Bitcoin in SSP and then come back here.

The fee unit: sat/vB

Bitcoin fees are quoted in sat/vB — satoshis per virtual byte. A satoshi is the smallest unit of Bitcoin (one hundred-millionth of a BTC). A virtual byte is a measure of how much room your transaction takes up in a block.

The key thing to internalise: you do not pay per dollar of value moved. You pay per byte of data. Sending 0.001 BTC and sending 5 BTC can cost the exact same fee if the transactions are the same size. What changes the size — and therefore the fee — is how many inputs and outputs the transaction has, and what kind of wallet produced it.

Your total fee is simply transaction size in vBytes × fee rate in sat/vB. A 200 vByte transaction at 20 sat/vB costs 4,000 satoshis. Pick a higher rate and it confirms sooner; pick a lower rate and it waits.

The mempool is a live fee market

When you broadcast a transaction, it does not go straight into the blockchain. It lands in the mempool — the pool of unconfirmed transactions that every Bitcoin node holds in memory. Miners build the next block by picking transactions from the mempool, and they are economically rational: they pick the highest-fee transactions first.

A new block arrives roughly every ten minutes and has limited space. When few people are transacting, the mempool is nearly empty and even a low fee gets you into the next block. When many people are transacting at once, the mempool backs up, and only transactions bidding above the going rate make it into the next block. Everyone else waits — sometimes for hours, sometimes for days, until demand cools and their bid becomes competitive again.

This is why fees swing. There is no central price. The "right" fee is whatever the current set of competing transactions makes it.

Reading a fee estimator

You do not have to guess. A fee estimator reads the current mempool and tells you what rate buys what speed. The most widely used public explorer is mempool.space, which shows the mempool depth and live recommendations in tiers — typically "next block", "within 30 minutes", and "within an hour or more" — each with a sat/vB number.

SSP surfaces a fee choice when you build a transaction so you can match your urgency to current conditions. The mental model is straightforward:

• Calm mempool. When the estimator's "next block" and "low priority" tiers are close together — often in the low single digits of sat/vB — there is no congestion. Pick the economy tier. Paying 40 sat/vB when 3 sat/vB would confirm in the next block is simply burning money.
• Congested mempool. When the tiers spread far apart and the "next block" number is high, the network is busy. If your payment is genuinely time-sensitive, pay the higher rate. If it is not, choose a lower tier and accept that it may take a few hours, or wait for a quieter window — fees are usually lower on weekends and overnight in the major-market time zones.

RBF: bumping a stuck transaction

Suppose you underpaid. The mempool got busier after you broadcast, your fee is no longer competitive, and your transaction has been stuck for hours. You are not powerless.

Replace-By-Fee (RBF) lets you re-broadcast the same transaction with a higher fee. The replacement spends the same inputs to the same recipient, so no extra money leaves your wallet beyond the increased fee — it simply overrides the original in the mempool. Miners then prefer the higher-fee version, and the low-fee original is dropped.

In SSP this matters in a particular way: your wallet is a 2-of-2 multisig, so every transaction — including an RBF bump — must be signed on both devices: your phone and your SSP Key. Bumping a fee is not a one-tap action; treat it as a fresh signing ceremony on two devices. Plan for that if a payment is urgent and you are away from your second device.

The alternative tool is CPFP (Child-Pays-For-Parent): instead of replacing the stuck transaction, you spend its unconfirmed output in a new high-fee transaction, and a miner who wants the child's fee must confirm the parent too. CPFP is mainly useful for incoming funds you cannot replace. For your own outgoing payments, RBF is usually the cleaner fix.

The multisig wrinkle

A 2-of-2 multisig transaction is larger in vBytes than a single-signature one, because it carries two signatures and a more complex spending script instead of one. SSP uses native SegWit multisig (P2WSH), which keeps that overhead modest, but the transaction is still bigger than a basic single-sig payment — so at the same sat/vB rate it costs somewhat more.

This is the price of removing the single-point-of-failure that a one-key wallet has, and it is small relative to the security you gain. Two practical consequences:

• When you compare an SSP fee to a fee you saw in a single-signature wallet, expect SSP's to be a bit higher at the same rate. That is the script, not an SSP markup.
• The more inputs (UTXOs) a transaction consumes, the larger it gets. If your balance is made up of many small receipts, spending it is expensive. The fix is UTXO consolidation — see Consolidating UTXOs in SSP.

Common pitfalls

• Overpaying in a quiet mempool. The single most common waste. Always glance at the estimator before accepting a default high fee; in calm conditions the economy tier confirms just fine.
• Underpaying and getting stuck. The opposite error. A fee that looked fine an hour ago can fall below the going rate as the mempool fills. If a payment matters, do not bid at the very bottom.
• Not knowing RBF exists. Many users assume a stuck transaction is lost and panic. It is not lost — it is unconfirmed, and it can be bumped or it will eventually drop from the mempool and the coins return to your wallet as spendable. Patience or an RBF bump both work.
• Forgetting the second device. Because bumping a fee is a full multisig signing, an urgent RBF needs your SSP Key on hand. Keep it accessible when you expect to send time-sensitive payments.

Putting it together

Before you send Bitcoin from SSP, check the mempool, match your fee tier to how urgent the payment is, and remember that you can always bump later with RBF if conditions change. When you are ready to make a payment, the step-by-step walkthrough is in Sending Bitcoin with SSP. To understand the other side of the ledger — fees and outputs when money comes in — read Receiving Bitcoin into SSP.

Fees are not a tax you cannot influence. They are a market you can read. A few seconds spent looking at the mempool turns fee-setting from a guess into a decision.