--- order: 13 --- # Light Client Light clients are an important part of the complete blockchain system for most applications. Tendermint provides unique speed and security properties for light client applications. See our [light package](https://pkg.go.dev/github.com/tendermint/tendermint/light?tab=doc). ## Overview The objective of the light client protocol is to get a commit for a recent block hash where the commit includes a majority of signatures from the last known validator set. From there, all the application state is verifiable with [merkle proofs](https://github.com/tendermint/spec/blob/953523c3cb99fdb8c8f7a2d21e3a99094279e9de/spec/blockchain/encoding.md#iavl-tree). ## Properties - You get the full collateralized security benefits of Tendermint; no need to wait for confirmations. - You get the full speed benefits of Tendermint; transactions commit instantly. - You can get the most recent version of the application state non-interactively (without committing anything to the blockchain). For example, this means that you can get the most recent value of a name from the name-registry without worrying about fork censorship attacks, without posting a commit and waiting for confirmations. It's fast, secure, and free! ## Where to obtain trusted height & hash [Trust Options](https://pkg.go.dev/github.com/tendermint/tendermint/light?tab=doc#TrustOptions) One way to obtain semi-trusted hash & height is to query multiple full nodes and compare their hashes: ```bash $ curl -s https://233.123.0.140:26657:26657/commit | jq "{height: .result.signed_header.header.height, hash: .result.signed_header.commit.block_id.hash}" { "height": "273", "hash": "188F4F36CBCD2C91B57509BBF231C777E79B52EE3E0D90D06B1A25EB16E6E23D" } ``` ## Running a light client as an HTTP proxy server Tendermint comes with a built-in `tendermint light` command, which can be used to run a light client proxy server, verifying Tendermint RPC. All calls that can be tracked back to a block header by a proof will be verified before passing them back to the caller. Other than that, it will present the same interface as a full Tendermint node. You can start the light client proxy server by running `tendermint light `, with a variety of flags to specify the primary node, the witness nodes (which cross-check the information provided by the primary), the hash and height of the trusted header, and more. For example: ```bash $ tendermint light supernova -p tcp://233.123.0.140:26657 \ -w tcp://179.63.29.15:26657,tcp://144.165.223.135:26657 \ --height=10 --hash=37E9A6DD3FA25E83B22C18835401E8E56088D0D7ABC6FD99FCDC920DD76C1C57 ``` For additional options, run `tendermint light --help`.