What is CPFP? CPFP stands for Child-Pays-For-Parent. When a Bitcoin transaction is stuck because its fee is too low, you can spend one of its outputs in a new child transaction that pays a higher fee. To collect the child’s fee, a miner has to include the parent too, so the parent gets confirmed along with it. Unlike RBF, CPFP can be used by both the sender and the recipient.
How Does CPFP Work?
The child spends a UTXO created by the parent, so by the rules it can only confirm after the parent or in the same block. When selecting transactions, miners treat the parent and child as a package and rank them by their combined fee divided by their combined size. That means the child’s fee cannot just cover itself; it has to make up the parent’s shortfall as well, so the package’s overall fee rate reaches the current market level. The larger the parent and the lower its fee rate, the more the child has to pay.
When Should You Use CPFP?
The first case is when the recipient wants to speed things up. For example, an exchange receives a low-fee user deposit that the user cannot or will not speed up; the exchange can include that unconfirmed output in a fund sweeping transaction and pay enough fee. The second is when the sender’s original transaction did not enable RBF, or the sender would rather not re-sign a full replacement, so they launch CPFP from their own change output. The third is when several deposits or payments are stuck at once: one child transaction can spend all their outputs and get them confirmed together.
What Is the Difference Between CPFP and RBF?
RBF replaces the original transaction: only the sender can do it, it spends the same inputs, and the new transaction is the one that confirms. CPFP adds a child after the original, which stays unchanged, and both the sender and the recipient can do it. RBF is usually cheaper because only one transaction goes on-chain; CPFP adds a second transaction, so total fees are generally higher, but it does not depend on whether the original is replaceable. Whichever method a business uses, the speed-up is a new signature and should go through the approval workflow.
Conclusion
CPFP uses a high-fee child transaction to get a stuck parent confirmed along with it. Both senders and recipients can use it, and it is especially useful for exchanges dealing with stuck deposits. The child’s fee should be calculated from the overall fee rate of the parent and child together. Safeheron’s Wallet-as-a-Service provides businesses with MPC key management and a policy engine.
Want smoother handling of Bitcoin deposits and sweeping? Contact Safeheron’s Sales Team to Book a 1:1 Demo
Looking for a secure way to manage digital assets?
Talk to our experts and find the right solution for your business.
Request a DemoLooking for a secure way to manage digital assets?
Talk to our experts and find the right solution for your business.