Regtest

Regtest, short for regression test mode, is a private bitcoin network mode in which a developer runs a local blockchain from scratch and creates blocks instantly on command rather than waiting for proof-of-work. A single machine can spin up a fresh chain, mine 100 blocks in seconds, and fund test wallets with coins that have no value anywhere else.

Why it matters

Software that moves money cannot be tested on money. Regtest gives wallet developers, exchanges, and protocol engineers a deterministic sandbox where every scenario is reproducible: block reorganizations can be triggered deliberately, timelocks can be fast-forwarded, and edge cases can be replayed until fixed. Bitcoin Core's own automated test suite runs on regtest, as do the continuous integration pipelines of most serious bitcoin projects.

How it works

Starting a node with the regtest flag creates an isolated chain with its own genesis block and a proof-of-work difficulty so low that blocks are generated by a simple command. The standard rules otherwise apply: coinbase rewards mature after 100 blocks, halvings occur on an accelerated schedule, and consensus checks run as they would on mainnet. Multiple regtest nodes can be connected to simulate network behavior, including partitions and competing chains. Regtest sits at the fully private end of bitcoin's test spectrum, alongside the public testnet and the more controlled signet.