This document explains how to use Klaytn APIs. Most APIs except Toolkit API support remote protocols (RPC, Websocket) and Klaytn JavaScript Console. This document is written with ken as an example but most of APIs can be used on kcn and kpn as well.

NOTE: Since few APIs do not support both of remote protocols and Klaytn JavaScript console, APIs available in remote protocols are documented mainly. Rest of APIs will be documented later.

Enabling APIs

To offer the APIs over the Klaytn RPC endpoints, please specify them with the --${interface}api command line argument where ${interface} can be rpc for the HTTP endpoint or ws for the WebSocket endpoint.

ipc offers all APIs over the unix socket (Unix) or named pipe (Windows) endpoint without any flag.

You can launch a Klaytn node with specific APIs you want to add like the example below. But keep in mind that you can't change APIs once you launch the node.

Example) launching a Klaytn node with klay and net modules enabled:

$ ken --rpcapi klay,net --rpc --{other options}

The HTTP RPC interface must be explicitly enabled using the --rpc flag.

NOTE: Offering an API over the HTTP (rpc) or WebSocket (ws) interfaces will give everyone access to the APIs who can access this interface (DApps, browser tabs, etc). Be careful which APIs you enable. By default Klay enables all APIs over the IPC (ipc) interface but for rpc and ws required modules have to be explicitly enabled.

To determine which APIs an interface provides, the modules JSON-RPC method can be invoked. For example over an rpc interface:


$ echo '{"jsonrpc":"2.0","method":"rpc_modules","params":[],"id":1}' | nc -U klay.ipc


$ curl -H "Content-Type: application/json" --data '{"jsonrpc":"2.0","method":"rpc_modules","params":[],"id":1}' https://public-en-baobab.klaytn.net

will give all enabled modules including the version number:


Disabling unsafe debug APIs

Some debug namespace APIs are unsafe/unappropriate to be opened to public. We recommend you to provide the debug namespace APIs to authorized users only. However, if you want to maintain a public EN and provide debug namespace APIs to the public, we strongly recommend you to set the rpc.unsafe-debug.disable flag which will disable APIs that are unsafe/unappropriate to be opened to the public and enable only a subset of the debug namespace APIs.

All other debug namespace APIs EXCEPT FOR the following APIs are restricted with rpc.unsafe-debug.disable flag:

  • VM Tracing APIs, however with limited functionality (only pre-defined tracers are allowed)

  • debug_dumpBlock, debug_dumpStateTrie, debug_getBlockRlp, debug_getModifiedAccountsByHash, debug_getModifiedAccountsByNumber, debug_getBadBlocks, debug_getModifiedStorageNodesByNumber

  • debug_metrics

To set the rpc.unsafe-debug.disable flag, append the following line in the kend.conf file.

ADDITIONAL="$ADDITIONAL --rpc.unsafe-debug.disable"

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