> ## Documentation Index
> Fetch the complete documentation index at: https://voltaire.tevm.sh/llms.txt
> Use this file to discover all available pages before exploring further.

# Event.encodeTopics

> Encode indexed event parameters into topic arrays

## Overview

`Event.encodeTopics` builds the topics array for an event filter. It includes `topic0` (the event selector) for non-anonymous events and encodes indexed parameters as topics.

## Quick Start

```typescript theme={null}
import { Abi } from '@tevm/voltaire/Abi';
import { Hex } from '@tevm/voltaire/Hex';

const Transfer = {
  type: 'event',
  name: 'Transfer',
  inputs: [
    { type: 'address', name: 'from', indexed: true },
    { type: 'address', name: 'to', indexed: true },
    { type: 'uint256', name: 'value' }
  ]
} as const;

const topics = Abi.Event.encodeTopics(Transfer, {
  from: '0x742d35Cc6634C0532925a3b844Bc9e7595f51e3e',
  to: '0x5B38Da6a701c568545dCfcB03FcB875f56beddC4'
});

const topicHex = topics.map((t) => (t ? Hex.fromBytes(t) : null));
```

## Wildcards and Partial Filters

Set an indexed value to `null` (or omit it) to leave that topic unconstrained:

```typescript theme={null}
const topics = Abi.Event.encodeTopics(Transfer, {
  from: null,
  to: '0x5B38Da6a701c568545dCfcB03FcB875f56beddC4'
});
```

## Use in Log Filters

`encodeTopics` returns byte arrays. Convert to hex strings when passing to JSON-RPC:

```typescript theme={null}
const topics = Abi.Event.encodeTopics(Transfer, {
  from: null,
  to: '0x5B38Da6a701c568545dCfcB03FcB875f56beddC4'
});

const filterTopics = topics.map((t) => (t ? Hex.fromBytes(t) : null));

const logs = await provider.getLogs({
  address: tokenAddress,
  topics: filterTopics
});
```

## Dynamic Indexed Parameters

Dynamic types (`string`, `bytes`, dynamic arrays, tuples with dynamic parts) are **hashed** with keccak256 before being placed in a topic. You cannot recover the original value from the topic alone.

## Anonymous Events

Anonymous events omit `topic0`. `encodeTopics` will return only the indexed parameter topics.

## See Also

* [decodeLog](/primitives/abi/event/decode-log) - Decode log data + topics
* [getSelector](/primitives/abi/event/get-selector) - Compute topic0 selector
* [Selectors](/primitives/abi/selectors) - Selector rules