Subscribing to events via Websocket

CometBFT emits different events, which you can subscribe to via Websocket. This can be useful for third-party applications (for analysis) or for inspecting state.

List of events

To connect to a node via websocket from the CLI, you can use a tool such as wscat and run:

wscat -c ws://

NOTE: If your node’s RPC endpoint is TLS-enabled, utilize the scheme wss instead of ws.

You can subscribe to any of the events above by calling the subscribe RPC method via Websocket along with a valid query.

    "jsonrpc": "2.0",
    "method": "subscribe",
    "id": 0,
    "params": {
        "query": "tm.event='NewBlock'"

Check out API docs for more information on query syntax and other options.

You can also use tags, given you had included them into FinalizeBlock response, to query transaction results. See Indexing transactions for details.

Query parameter and event type restrictions

While CometBFT imposes no restrictions on the application with regards to the type of the event output, there are several considerations that need to be taken into account when querying events with numeric values.

Prior to version v0.38.x, floats were not supported as query parameters.


When validator set changes, ValidatorSetUpdates event is published. The event carries a list of pubkey/power pairs. The list is the same CometBFT receives from ABCI application (see EndBlock section in the ABCI spec).


    "jsonrpc": "2.0",
    "id": 0,
    "result": {
        "query": "tm.event='ValidatorSetUpdates'",
        "data": {
            "type": "tendermint/event/ValidatorSetUpdates",
            "value": {
              "validator_updates": [
                  "address": "09EAD022FD25DE3A02E64B0FE9610B1417183EE4",
                  "pub_key": {
                    "type": "tendermint/PubKeyEd25519",
                    "value": "ww0z4WaZ0Xg+YI10w43wTWbBmM3dpVza4mmSQYsd0ck="
                  "voting_power": "10",
                  "proposer_priority": "0"
Decorative Orb