> For the complete documentation index, see [llms.txt](https://docs.chainargos.com/documentation/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://docs.chainargos.com/documentation/concept-glossary/address-types/genesis-or-built-in-contract.md).

# Genesis or "Built-In" Contract

Some smart contracts are built in to blockchains when the code is written rather than being deployed by users later. These are not verified in the normal public sense. And we cannot blindly trust these addresses even act in accordance with the general system rules. All must be checked.

For example we can look at:

* [Token Hub on BSC](https://bscscan.com/address/0x0000000000000000000000000000000000001004)
* [WETH on Base](https://basescan.org/address/0x4200000000000000000000000000000000000006)

The former acts like a smart contract that effects a bridge to the BNB Beacon chain while the later acts like a token contract. In both cases notice the creator is "GENESIS." That means the contract appeared at block 0 and was never properly deployed by anyone.

These contracts can, in theory, do anything and need not respect the system rules. And there is no on-chain code to inspect -- we need to read the node code.

Note that Ethereum has no such contracts. And generally network with built-in functionality like this are more likely to be more centralized than networks without them.

For both of the examples given here the built-in contracts form part of a cross-chain communication scheme under the control of the system's sole operator.


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