Introduction to Avalanche Subnets
July 1, 2022

By Andrew Allen, Protocol Specialist
Most people know Avalanche as an EVM-compatible blockchain that has gained significant traction. However, there is much more to Avalanche, including many more blockchains!
Many Avalanche users are only familiar with the C-Chain, which forked the Ethereum Geth client to add support for the Ethereum Virtual Machine (EVM), but there are actually 3 chains in Avalanche’s Primary Network. But in addition, one of Avalanche’s core innovations is the ability to create highly scalable and customizable blockchains called Subnets.
With limited blockspace and demand rising, fees have risen on the C-Chain. And while there are improvements that can be made, scaling to meet demand requires more blockspace or more efficient use of existing blockspace (i.e. off-chain computation via Layer 2s). Subnets are Avalanche’s solution to this problem.
Instead of forcing all transactions to take place on a single, shared state, Subnets allow developers to launch their own blockchains– creating more blockspace and computation to meet demand.
What's a Subnet?
Subnets, or subnetworks, are a dynamic subset of Avalanche validators that reach consensus on their own blockchains. This definition can feel somewhat formal, so jargon aside, Subnets are effectively ‘Blockchain-as-a-Service’ secured by some portion of Avalanche validators. Put another way, a Subnet is not a blockchain; a Subnet is a group of validators. Today, all Subnets (other than the Primary Network) run a single blockchain, but it is possible for future Subnets to run multiple blockchains.
Avalanche validators don’t automatically run blockchains for any Subnet. Instead, Subnets need to incentivize Avalanche validators separately for their support. Since Subnets can have their own economies with their own native tokens and fee markets, it is likely that Subnet validators will stake and be rewarded in a Subnet’s native token.
Once an Avalanche validator creates a Subnet, the Subnet can create rulesets for their validators and launch their own blockchains with customized virtual machines. Since the developers are able to customize various aspects of how the underlying chain operates, they can also implement features like sending gas fees to a treasury smart contract or requiring all users of a chain to pass through KYC before interacting with applications on the Subnet.
It was originally envisioned that Subnets would be a hub for financial markets to launch highly customized and permissioned systems. However, in practice many of the current teams interested in launching Subnets are looking to scale their existing applications, which might be limited by their current chain.
These live projects limited by their current chain might not be as interested in modifying the underlying blockchain. For these builders, they can simply run a copy of an existing virtual machine, deploy their existing contracts, and let users interact with nearly identical applications on their own blockchain. This approach requires little incremental development on the part of the application developers, and the application immediately unlocks further throughput at low transaction costs.

Launching an EVM Chain on your own Subnet as viewed by Avascan
Secret sauce - why build on Avalanche?
The Avalanche ecosystem has grown popular over the past year for a number of reasons and quite a few of Avalanche’s strong points are directly applicable to prospective Subnets. Each of the following functionalities can be leveraged by Subnets launching their own blockchain:
Fast finality: Avalanche’s consensus mechanism is unique in that it reaches finality on a transaction within a single block, which typically takes 2 seconds on the C-Chain. Similarly, Subnets can achieve this fast finality on their blockchains by using Avalanche