---
title: Content Topic and How to Choose One
---

A content topic is used for content based filtering and allows you to filter out the messages that your dApp processes,
both when receiving live messages (Relay or Filter) or retrieving historical messages (Store).

The recommended format for content topics is as follows:

`/{dapp-name}/{version}/{content-topic-name}/{encoding}`

- `dapp-name`: The name of your dApp, it must be unique to avoid conflict with other dApps.
- `version`: We usually start at `1`, useful when introducing breaking changes in your messages.
- `content-topic-name`: The actual content topic name to use for filtering.
  If your dApp uses Waku for several features,
  you should use a content topic per feature.
- `encoding`: The encoding format of the message, [Protobuf](https://developers.google.com/protocol-buffers) is most often used: `proto`.

For example: Your dApp's name is SuperCrypto,
it enables users to receive notifications and send private messages.
You may want to use the following content topics:

- `/supercrypto/1/notification/proto`
- `/supercrypto/1/private-message/proto`

## PubSub topic

There is another type of a _topic_ in Waku: A pubsub topic is used for routing of messages between the relaying nodes in the Waku network.

> This section talks more about how networking and relaying of messages is handled by the nodes in the network,
> and has little to do with the application layer of Waku.
> Feel free to skip ahead this section if you are not interested in the details of how Waku works.

The format for a pubsub topic is as follows:
`/waku/2/{topic-name}/{encoding}` and the default pubsub topic is `/waku/2/default-waku/proto`.

This indicates to:

1. `waku`: Waku problem domain
2. `2`: Version is 2
3. `default-waku`: Default topic for exchanging WakuMessages
4. `proto`: The data field in PubSub is serialized/encoded as Protobuf as determined by WakuMessage

Unless there’s a good reason, the default PubSub topic is used for all protocols. However, in certain situations other topics may be used.

Using a single PubSub topic ensures a connected network, as well some degree of metadata protection. See [Anonymity/Unlinkability](https://rfc.vac.dev/spec/10/#anonymity--unlinkability) for more details.