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OpenSats is funding nine more open-source projects advancing the Bitcoin ecosystem.
Testnet
testnet3, testnet4, Bitcoin testnet
Bitcoin’s public test network, where developers can broadcast valueless coins and exercise software against shared network conditions.
Testnet is Bitcoin’s public testing network. It uses separate coins with no intended monetary value, so developers can test wallets, nodes, transaction flows, and protocol changes without risking mainnet funds.
Because testnet is public, anyone can join it, mine blocks, and broadcast transactions. That makes it useful for interoperability testing between independent teams and for demos that need a shared network instead of a local sandbox.
The tradeoff is reliability. Testnet has historically suffered from spam, unstable block production, and resets between generations. That is one reason many teams now use Signet for coordinated multi-party testing when they need a more predictable environment.
As of mid-2026, the active public network is Testnet4, as defined by BIP 94. Earlier generations were reset after long periods of instability or abuse.