A zParachain is an approach to bridging where a dedicated blockchain in the broader Polkadot ecosystem is used specifically to connect to a network that’s outside the Polkadot ecosystem.

What Is zParachain

A zParachain is an approach to bridging where a dedicated blockchain in the broader Polkadot ecosystem is used specifically to connect to a network that’s outside the Polkadot ecosystem. It uses a bridging technique where both chains only need to agree on block headers.

Bridging, in General

With so many different approaches to layer 1 networks, as well as a budding layer 2 sector with sidechains, appchains, and modular solutions, it seems as if the space is becoming more and more fragmented. As a result, various forms of interoperability solutions have become essential components of the overall web3 infrastructure.
Chief among these is bridging. As previously defined: “A blockchain bridge is a protocol that outlines minting and burning procedures so that the token supply can be constant between two different platforms. Bridges serve as a transition between the different blockchain protocols. When a token is locked up in one of the blockchain protocols, its equivalent is minted on the second blockchain, allowing interoperability between two completely different protocols. This transfer happens under the mint-and-burn protocol.
Bridges became most popular during the 2017 DeFi Summer with the rise of trading strategies such as yield farming. During this time, users sought to take advantage of opportunities for liquidity provision that were popping up across different web3 ecosystems. Successful execution of these strategies required users to move funds between different networks.

Over time, many ecosystems dedicated their efforts to developing efficient bridging strategies to ensure that they had access to the liquidity in other ecosystems as quickly as possible. Thanks to bridges, there is now an increasingly interconnected economy between all of these web3 ecosystems.

The Light-Client Approach to Bridging

Bridges are not a one-size-fits-all solution, however. As one would expect, every ecosystem has its own rules and parameters for what constitutes a valid bridging mechanism. Some ways of doing this have become more popular than others, starting with validator-based bridges, liquidity-based bridges, and light client bridges.

zParachains are a specific approach to light client bridging. In light client bridging, we have a system where a group of “guardians” are tasked with monitoring and reporting events from one chain (a source chain) to another (a destination chain). 

What happens is that these “guardians” send over block headers to a light client on the destination chain. This way, the destination chain only needs to store the necessary information to verify the corresponding transactions. Once the events are approved on both networks, users are free to withdraw their funds. 

In the case of zParachains, the destination chain would be parachain in the Polkadot ecosystem, hence the name.

So, What Is a zParachain Exactly?

Let’s start with what a parachain is. Polkadot is a “blockchain of blockchains'' that allows many different chains to interact securely with one another. The independent layer-1 blockchains that operate within Polkadot’s multi chain ecosystem are known as parachains.
Parachains can be built to serve specific purposes as long as they conform to the Substrate framework and connect to Polkadot’s main chain (known as the Relay Chain). This guarantees compatibility with the rest of the ecosystem. One of these specific purposes, of course, can be bridging with other networks outside of Polkadot.

A zParachain is simply a parachain that acts as a bridge between Polkadot and an external ecosystem.

zParachains in Action

The first use of a zParachain will be defined by its implementation between Polkadot and the Aleph Zero ecosystem. While Aleph Zero (AZERO) itself is not a parachain, the network leases an intermediary parachain that is used only for bridging purposes. 

Aleph Zero is completely compatible with Substrate, therefore its zParachain operates seamlessly within the Polkadot ecosystem. Likewise, since this type of bridge is based on the light-client approach mentioned above, the finality of transactions from the source chain can be verified on the destination chain without requiring a third-party component. This guarantees that the bridge operates in a fully trustless manner.

zParachains are a bridging strategy that’s particular to Polkadot and how it works with other ecosystems. However, they aim to offer versatility, stability, and several options to choose from, depending on who the end user is since their implementation can be customized to the needs of the source chain.

The Future of Bridging

As more ecosystems bud and grow, so will the interoperability solutions that are designed to fit their particular needs. zParachains point to a future where even generalized bridging strategies such as light client bridging are increasingly customizable to serve the needs of specific ecosystems and communities.