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 project complete control, built using Polygon’s Chain Development Kit, known as the CDK.
Starting in 2026, Polygon has repositioned CDK from a self-service open-source toolkit to an enterprise-grade managed 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 allows teams to 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 necessary components and then launches a chain that fits its specific use case.
Every chain built with the CDK uses zero-knowledge proofs, a cryptographic method that allows one party to prove something is true without revealing the underlying data. This keeps transactions verifiable and secure without sending all transaction data directly to Ethereum.
An important distinction worth knowing: Polygon’s own zkEVM product, which was a separate public chain, launched on July 1, 2026. That’s different from CDK-based custom chains, which remain fully active and unaffected by that shutdown. Projects like X Layer and Immutable zkEVM run on the CDK infrastructure, not on Polygon’s legacy zkEVM chain.
Is the Polygon CDK still free and open source?
This is where things have changed significantly since the early days of CDK.
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-service kit.” Projects work directly with Polygon Labs to design, build and operate a custom chain. Implementation partners, including Gateway and Conduit, manage production deployments with enterprise SLAs and 24/7 support.
This doesn’t mean CDK isn’t available to non-enterprise teams. But the current product offering is a managed service, not a toolkit that a team simply downloads and deploys independently.
Teams evaluating CDK must consider operational support, sequencer management, and infrastructure decisions as part of the equation, which is typically handled with Polygon and its partners.
How does a custom chain actually work?
Each CDK chain arranges its transactions on Ethereum. This means that Ethereum’s security supports the chain, even though the chain itself operates independently.
This is what a project can configure when building with the CDK:
- The gas token, that is, the currency used to pay transaction fees for that chain
- The data availability layer, which determines where transaction data is stored
- The execution environment, which determines what type of smart contracts the chain executes
- The sequencer, the part that orders transactions
- Privacy controls, including the availability of private data and role-based access for regulated use cases
This level of control is important for projects that require low costs, quick finality or a specific token as the native gas currency. For example, a gaming project might want its own token to pay for gas instead of ETH. An institution that handles payments may need configurable privacy controls and compliance tools baked into the chain at launch.
Chains built with the CDK are connected via the AggLayer, Polygon’s interoperability protocol. AggLayer allows assets and data to move between CDK chains without having to go back through Ethereum, reducing costs and accelerating cross-chain activity. AggLayer is now a core part of Polygon’s infrastructure, actively used across multiple deployed chains, and is no longer in early development.
Who already uses 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 used $OKBOKX’s native token, as its guest token. In August 2025, X Layer completed a major performance upgrade known as the Pessimistic Proof upgrade, increasing throughput to 5,000 transactions per second and further reducing gas costs. X Layer connects to AggLayer and serves OKX’s more than 50 million users as the 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 own gas token and reached 2 million monthly active users within its first year of mainnet operation. Active titles on the platform include RavenQuest, which attracted more than 1 million unique viewers on Twitch ahead of 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, has also migrated its infrastructure to a CDK-based chain and focused on tokenization of real-world assets through AggLayer.
What are the tradeoffs?
Running a tailor-made chain entails 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 fragmentation. The more chains that exist, the more difficult 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 in active chains such as X Layer and Katana Network, a DeFi-targeted CDK chain incubated by Polygon Labs, shows that 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 via AggLayer. The product has grown from an open-source toolkit to a managed business service, changing the way teams need to plan a deployment.
Real-world examples from OKX, Immutable and Astar confirm that the infrastructure works at scale. Teams considering CDK today must consider the managed service model and evaluate operational requirements alongside technical capabilities.
- Polygoon 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 on the CDK architecture, execution stacks, merge modes, and deployment guidelines.
- Polygon AggLayer – How Polygon’s interoperability layer connects CDK chains and enables cross-chain asset movement.
- Announcing OKX X Layer PP upgrade – OKX’s official announcement about the X Layer performance upgrade in August 2025, covering throughput improvements and $OKB changes in the gas fuel.
- Immutable zkEVM status from Q1 2025, Messari – Independent analysis of Immutable zkEVM’s transaction activity, user growth and CDK infrastructure.
- Ubisoft is working with Immutable on Might and Magic Fates – Official announcement that Ubisoft is building on Immutable zkEVM, including ecosystem milestones.
- Polygon zkEVM sunset page – Polygon’s official page confirms the sunset of Polygon zkEVM Mainnet Beta on July 1, 2026 and the asset migration process.