Introducing Rococo: Polkadot’s Parachain Testnet

Earlier this week, we reached a significant step towards implementing parachain functionality on Polkadot — we launched a new testnet specifically designed for parachains and their related technologies, dubbed Rococo. The Rococo testnet integrates Polkadot with Cumulus and HRMP (Horizontal Relay-chain Message Passing).

With Rococo, parachain developers can:

• Register a Substrate-based chain as a parachain and message the Relay Chain.
• Write logic for parachains to send messages to other parachains through the Relay Chain.

Rococo is designed strictly for testing parachain functionality. We also intend for Rococo to be a testbed for developing the Cross-Consensus Message (XCM) format, and are looking forward to gathering feedback from our community of parachain builders.

Rococo will launch as a Proof of Authority (PoA) network, with a Sudo key controlled by the parachain development leads at Parity Technologies. Rococo will include three parachains that support sending messages to the Relay Chain, and messages between each other through the relay chain.

Rococo will be reset multiple times to follow recent versions and maintain stability. Rococo does not guarantee a full, stable feature-set at this time, and functionality such as HRMP may be removed and re-added as we fix bugs and progress the codebase. Functions like XCMP (Cross-Chain Messaging Passing, enabling direct parachain-to-parachain messaging) and “hot-swapping” an independently running Substrate chain with a parachain are not yet activated. However, these features are planned for a future release of Cumulus on Rococo.

We look forward to seeing the hard work put in by parachain teams around the world in action on Rococo’s Relay Chain!