> For the complete documentation index, see [llms.txt](https://docs.butternetwork.io/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://docs.butternetwork.io/zk-light-client/understanding-light-client.md).

# Understanding Light Client

### Backgroud

Light Clients function by downloading only the block headers of a blockchain rather than the full block data. Block headers contain a summary of the block, including its hash, the hash of the previous block, and a unique identifier called the Merkle root. By using this information, light clients can verify if a particular transaction is included in a block without needing the entire block data.

When a light client wants to confirm a transaction, it requests Merkle proofs from full nodes. These proofs can mathematically verify that a transaction is part of a block, using a tiny amount of data. This efficiency makes light clients ideal for devices with limited storage or bandwidth, such as smartphones or IoT devices.

<figure><img src="/files/L8xj3gV08WL4iQmm3bEs" alt=""><figcaption></figcaption></figure>

### Issues with Light Client Verification

Although light client verfication is more secure and decentralized than solutions such as Multi-Party Computation (MPC), the amount of gas fee consumption with light clients verification network is more costly, which will not be efficient and practical enough to serve for cross-chain purposes. To improve efficiency, light clients can instead validate a ZK-SNARK proof that a block header is valid.