# Message counting

Messages are the primary unit of consumption that Ably charges for. Understanding which operations count as messages helps you estimate and manage costs.

## How Ably counts messages 

As a general rule, most operations involve publishing and receiving messages. Each operation generates:

* 1 inbound message when a client publishes or performs an operation
* 1 outbound message for each subscriber that receives it

For example, if 1 client publishes a message to a channel with 10 subscribers, this counts as **11 messages** (1 inbound + 10 outbound).

By default, [echo messages](https://ably.com/docs/pub-sub/advanced.md#echo) are enabled, which means the publisher also receives its own message as an outbound delivery. In the example above, echo adds 1 outbound message for a total of **12 messages**.

Client-side [message filtering](https://ably.com/docs/api/realtime-sdk/channels.md#subscribe), where a subscribe callback selectively processes messages, does not reduce your message count. Ably delivers all messages on a channel to every subscriber regardless of client-side filtering. To filter messages server-side and reduce outbound message counts, use [subscription filters](https://ably.com/docs/pub-sub/advanced.md#subscription-filters).

The tables below list all operations that count as messages. Unless noted otherwise, each operation follows this inbound/outbound pattern. `Time` and `Ping` operations are not counted.

## Message size 

Ably calculates message size as the sum of the `name`, `clientId`, `data`, and `extras` [properties](https://ably.com/docs/api/realtime-sdk/messages.md#properties) before any compression or expansion occurs in the serialization process. This applies to all products built on Pub/Sub, including Chat.

* `name` and `clientId` are calculated as the size in bytes of their UTF-8 representation.
* `data` is calculated as the size in bytes if it is binary, or its UTF-8 byte length if it is a string.
* `extras` is calculated as the string length of its JSON representation.

Ably bills messages in 5KiB chunks. A message up to 5KiB counts as 1 message. A 50KiB message counts as 10 messages, and a 16KiB message counts as 4 messages.

Each package has a bandwidth allowance based on an average message size of 5KiB. If your total bandwidth for the month exceeds this baseline, Ably charges overage per GiB. See [maximum message size](https://ably.com/docs/platform/pricing/limits.md#message) for the size limits per package type.

## Pub/Sub operations 

The following table shows how [Pub/Sub](https://ably.com/docs/pub-sub.md) operations contribute to your message count:

| Operation | Messages counted |
| --- | --- |
| [Messages](https://ably.com/docs/channels/messages.md) ||
| Publish | 1 inbound message |
| Message delivery | 1 outbound message per subscriber |
| [Presence](https://ably.com/docs/presence-occupancy/presence.md) ||
| Presence enter | 1 inbound message |
| Presence leave | 1 inbound message |
| Presence update | 1 inbound message |
| Presence event delivery | 1 outbound message per presence subscriber |
| Presence REST query | 1 outbound message per member returned |
| Batch presence request | 1 outbound message per member across all queried channels |
| [Storage and history](https://ably.com/docs/storage-history/storage.md) ||
| Persistence storage | 1 additional message per stored message |
| History retrieval | 1 outbound message per retrieved message |
| [Rewind](https://ably.com/docs/channels/options/rewind.md) on attach | 1 outbound message per rewound message (up to 100) |
| [Integrations](https://ably.com/docs/platform/integrations.md) ||
| Integration delivery | 1 outbound message per integration target |
| [Inbound integration publish](https://ably.com/docs/platform/integrations.md#inbound) | 1 inbound message |
| [Push notifications](https://ably.com/docs/push.md) ||
| Push notification delivery | 1 outbound message per delivered notification |
| [Annotations](https://ably.com/docs/messages/annotations.md) ||
| Annotation publish | 1 inbound message |
| Annotation delete | 1 inbound message |
| [Annotation summary delivery](https://ably.com/docs/messages/annotations.md#annotation-summaries) | 1 outbound message per subscriber; multiple annotations may be rolled up into a single summary |
| [Metadata and stats](https://ably.com/docs/metadata-stats/metadata.md) ||
| Lifecycle event (`[meta]connection.lifecycle`, `[meta]channel.lifecycle`) | 1 outbound message per event |
| `[meta]stats:minute` event | 1 outbound message per event |
| `[meta]log` subscription | Not counted |

For Pub/Sub-specific cost optimization strategies, see [Pub/Sub pricing](https://ably.com/docs/pub-sub/pricing.md).

## Chat operations 

The [Chat SDK](https://ably.com/docs/chat.md) is built on top of [Pub/Sub](https://ably.com/docs/pub-sub.md). All Chat operations generate Pub/Sub messages that follow the same counting rules.

| Operation | Messages counted |
| --- | --- |
| [Messages](https://ably.com/docs/chat/rooms/messages.md) ||
| Send message | 1 inbound message |
| Message delivery | 1 outbound message per subscriber |
| Update message | 1 inbound message |
| Message update delivery | 1 outbound message per subscriber |
| Delete message | 1 inbound message |
| Message deletion delivery | 1 outbound message per subscriber |
| [History](https://ably.com/docs/chat/rooms/history.md) ||
| History retrieval | 1 outbound message per retrieved message |
| [Typing indicators](https://ably.com/docs/chat/rooms/typing.md) ||
| Typing keystroke | 1 inbound message; repeats every heartbeat interval (default 10s) |
| Typing keystroke delivery | 1 outbound message per subscriber per heartbeat |
| Typing stop | 1 inbound message |
| Typing stop delivery | 1 outbound message per subscriber |
| [Room reactions](https://ably.com/docs/chat/rooms/reactions.md) ||
| Room reaction | 1 inbound message |
| Room reaction delivery | 1 outbound message per subscriber |
| [Message reactions](https://ably.com/docs/chat/rooms/message-reactions.md) ||
| Message reaction send | 1 inbound message |
| Message reaction delete | 1 inbound message |
| Message reaction summary delivery | 1 outbound message per subscriber; multiple reactions may be rolled up into a single summary |
| [Presence](https://ably.com/docs/chat/rooms/presence.md) ||
| Presence enter | 1 inbound message |
| Presence leave | 1 inbound message |
| Presence update | 1 inbound message |
| Presence event delivery | 1 outbound message per presence subscriber |
| [Occupancy](https://ably.com/docs/chat/rooms/occupancy.md) ||
| Occupancy event | 1 outbound message per subscriber (generated on membership changes, debounced up to 15s) |
| [Moderation](https://ably.com/docs/chat/moderation.md) ||
| Moderation rule invocation (before or after publish) | 1 outbound webhook event per moderated message |

For Chat-specific cost optimization strategies, see [Chat pricing](https://ably.com/docs/chat/pricing.md).

## LiveObjects operations 

[LiveObjects](https://ably.com/docs/liveobjects.md) operations are billed using ObjectMessages. Each ObjectMessage follows the standard inbound/outbound counting pattern.

| Operation | Messages counted |
| --- | --- |
| [LiveMap](https://ably.com/docs/liveobjects/map.md) ||
| LiveMap set or remove | 1 inbound message per operation |
| LiveMap create (shallow) | 2 inbound messages (create + assign) |
| [LiveCounter](https://ably.com/docs/liveobjects/counter.md) ||
| LiveCounter increment or decrement | 1 inbound message |
| LiveCounter create | 2 inbound messages (create + assign) |
| ObjectMessage delivery | 1 outbound message per connected client |
| [Synchronization](https://ably.com/docs/liveobjects/pricing.md#synchronization) | 1 outbound message per object synchronized |
| [REST API](https://ably.com/docs/liveobjects/pricing.md#rest-api) fetch | 1 outbound message per object in response |
| [Batch](https://ably.com/docs/liveobjects/batch.md) operation | 1 inbound message per operation in the batch |

Nested object creation generates additional messages for each nested object.

For LiveObjects-specific cost optimization strategies, see [LiveObjects pricing](https://ably.com/docs/liveobjects/pricing.md).

## Spaces operations 

The [Spaces SDK](https://ably.com/docs/spaces.md) is built on top of [Pub/Sub](https://ably.com/docs/pub-sub.md) channels and [presence](https://ably.com/docs/presence-occupancy/presence.md). All Spaces operations generate Pub/Sub messages that follow the same counting rules.

| Operation | Messages counted |
| --- | --- |
| [Members](https://ably.com/docs/spaces/space.md) ||
| Enter space | 1 inbound message |
| Leave space | 1 inbound message |
| Update profile | 1 inbound message |
| Space event delivery | 1 outbound message per subscriber |
| [Locations](https://ably.com/docs/spaces/locations.md) ||
| Set location | 1 inbound message |
| Location event delivery | 1 outbound message per subscriber |
| [Cursors](https://ably.com/docs/spaces/cursors.md) ||
| Set cursor position | 1 inbound message per batch (default batch interval 25ms) |
| Cursor event delivery | 1 outbound message per subscriber |
| [Locking](https://ably.com/docs/spaces/locking.md) ||
| Acquire lock | 1 inbound message |
| Release lock | 1 inbound message |
| Lock event delivery | 1 outbound message per subscriber |

Live cursors use a [separate channel](https://ably.com/docs/spaces/cursors.md#foundations) from other space features due to their high update frequency. Registering multiple subscription listeners for the same event does not increase your message count, as these are [client-side filtered events](https://ably.com/docs/spaces/space.md#subscribe).

For Spaces-specific cost optimization strategies, see [Spaces pricing](https://ably.com/docs/spaces/pricing.md).

## LiveSync operations 

[LiveSync](https://ably.com/docs/livesync.md) publishes database changes as Pub/Sub messages. Each update follows the standard inbound/outbound counting pattern.

| Operation | Messages counted |
| --- | --- |
| Database update publish | 1 inbound message |
| Update delivery | 1 outbound message per subscriber |

For example, if the database connector publishes 1 update and 3 clients are subscribed, this counts as **4 messages** (1 inbound + 3 outbound).

For LiveSync-specific cost optimization strategies, see [LiveSync pricing](https://ably.com/docs/livesync/pricing.md).

## Related Topics

- [Overview](https://ably.com/docs/platform/pricing.md): Understand the pricing models available to you, and understand the benefits of each package type.
- [Billing](https://ably.com/docs/platform/pricing/billing.md): Understand how invoicing and billing works for Ably packages.
- [Limits](https://ably.com/docs/platform/pricing/limits.md): The limits associated with each Ably package.
- [Pricing FAQs](https://ably.com/docs/platform/pricing/faqs.md): A list of the most commonly asked questions related to Ably pricing.

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