Polygon gives developers a framework to build and launch their own blockchains that connect back to the Ethereum network. These chains are not forks or copies of Polygon itself. They are independent networks that projects control entirely, built using Polygon’s Chain Development Kit, known as the CDK.
As of 2026, Polygon has repositioned CDK from a self-serve open-source toolkit into a managed, enterprise-grade service, with real deployments running at scale from OKX, Immutable, and Astar Network.
What Is the Polygon CDK?
The Polygon CDK is a framework that lets teams build custom blockchains secured by zero-knowledge proofs and settled on Ethereum. Think of it as a modular construction kit. A project works with Polygon to configure the components it needs, then launches a chain that suits its specific use case.
Each chain built with the CDK uses zero-knowledge proofs, a cryptographic method that lets one party prove something is true without revealing the underlying data. This keeps transactions verifiable and secure without posting all transaction data directly to Ethereum.
One important distinction worth knowing: Polygon’s own zkEVM product, which was a separate public chain, set to sunset on July 1, 2026. That is different from CDK-based custom chains, which remain fully active and are unaffected by that shutdown. Projects like X Layer and Immutable zkEVM run on CDK infrastructure, not on Polygon’s deprecated zkEVM chain.
Is the Polygon CDK Still Free and Open Source?
This is where things have shifted significantly since CDK’s early days.
The underlying code remains open source under the GNU AGPL license on GitHub. However, Polygon has repositioned the product itself. As of 2026, Polygon’s official documentation describes CDK as “Chain-as-a-service, not a self-serve kit.” Projects work directly with Polygon Labs to design, build, and operate a bespoke chain. Implementation partners including Gateway and Conduit manage production deployments with enterprise SLAs and 24/7 support.
This does not mean CDK is unavailable to non-enterprise teams. But the current product offering is a managed service, not a toolkit a team simply downloads and deploys independently.
Teams evaluating CDK should factor in operational support, sequencer management, and infrastructure decisions as part of the equation, typically handled with Polygon and its partners.
How Does a Custom Chain Actually Work?
Every CDK chain settles its transactions on Ethereum. That means Ethereum’s security backs the chain, even though the chain itself operates independently.
Here is what a project can configure when building with the CDK:
- The gas token, meaning the currency used to pay transaction fees on that chain
- The data availability layer, which determines where transaction data is stored
- The execution environment, which controls what kind of smart contracts the chain runs
- The sequencer, which is the component that orders transactions
- Privacy controls, including private data availability and role-based access for regulated use cases
This level of control matters for projects that need low fees, fast finality, or a specific token as the native gas currency. A gaming project, for example, might want its own token to pay gas instead of ETH. An institution handling payments might need configurable privacy controls and compliance tooling baked into the chain at launch.
Chains built with the CDK connect to each other through the AggLayer, Polygon’s interoperability protocol. AggLayer lets assets and data move between CDK chains without going back through Ethereum each time, which reduces costs and speeds up cross-chain activity. AggLayer is now a core part of Polygon’s infrastructure, actively used across multiple deployed chains and no longer in early development.
Who Is Already Using It?
Several established projects have launched chains using the CDK.
OKX, one of the largest crypto exchanges by volume, launched X Layer using the Polygon CDK. X Layer uses $OKB, OKX’s native token, as its gas token. In August 2025, X Layer completed a major performance upgrade, known as the Pessimistic Proof upgrade, boosting throughput to 5,000 transactions per second and reducing gas fees further. X Layer connects to AggLayer and serves OKX’s more than 50 million users as its primary on-chain network.
Immutable, a platform focused on blockchain gaming and NFTs, built Immutable zkEVM with the CDK. The chain uses IMX as its native gas token and reached 2 million monthly active users within its first year of mainnet operation. Active titles on the platform include RavenQuest, which drew over 1 million unique viewers on Twitch before its global launch, and Ubisoft’s Might and Magic Fates, which is being built on Immutable zkEVM by one of the world’s largest game studios.
Astar Network, a Japanese blockchain project, also migrated its infrastructure to a CDK-based chain and has targeted tokenization of real-world assets through AggLayer.
What Are the Trade-offs?
Running a custom chain comes with real operational costs. Under the current CDK model, teams work with Polygon and its implementation partners to manage the sequencer, infrastructure, and ongoing upgrades. This lowers the technical barrier compared to building from scratch but introduces a dependency on Polygon’s managed ecosystem.
There is also a fragmentation consideration. The more chains that exist, the harder it can be for users to move assets between them without friction. AggLayer addresses this directly by routing liquidity and assets across CDK chains without requiring users to go through Ethereum each time. Its adoption across active chains like X Layer and Katana Network, a DeFi-focused CDK chain incubated by Polygon Labs, shows the interoperability layer is operational, not just planned.
Conclusion
Polygon’s CDK gives projects a concrete path to launching their own Ethereum-secured blockchains with configurable privacy, custom gas tokens, and built-in interoperability through AggLayer. The product has matured from an open-source toolkit into a managed enterprise service, which changes how teams should plan a deployment.
Real-world examples from OKX, Immutable, and Astar confirm the infrastructure works at scale. Teams considering CDK today should account for the managed service model and evaluate operational requirements alongside the technical capabilities.
- Polygon CDK Official Page – Official product page for Polygon CDK, covering the chain-as-a-service model, architecture, and institutional use cases.
- Polygon CDK Developer Documentation – Technical documentation covering CDK architecture, execution stacks, rollup modes, and deployment guidance.
- Polygon AggLayer – How Polygon’s interoperability layer connects CDK chains and enables cross-chain asset movement.
- OKX X Layer PP Upgrade Announcement – OKX’s official announcement on X Layer’s August 2025 performance upgrade, covering throughput improvements and $OKB gas token changes.
- Immutable zkEVM State of Q1 2025, Messari – Independent analysis of Immutable zkEVM’s transaction activity, user growth, and CDK infrastructure.
- Ubisoft Partners with Immutable on Might and Magic Fates – Official announcement of Ubisoft building on Immutable zkEVM, including ecosystem milestones.
- Polygon zkEVM Sunset Page – Polygon’s official page confirming the July 1, 2026 sunset of Polygon zkEVM Mainnet Beta and the asset migration process.
