![ably-logo-faqs-neg.png]](https://faqs.ably.com/hs-fs/hubfs/ably-logo-faqs-neg.png?height=40&name=ably-logo-faqs-neg.png){kind=logo}
Channels
Details on channel functionality, limits, and best practices
Messages
- I'm not receiving messages, how do I debug that?
- Can I see messages sent by Channel or ClientID?
- How does Ably count and bill for messages?
- How can I reduce my message count?
- Is it possible to check if a specific message has been delivered to a device?
- Reliable message ordering for connected clients
- Can a published message be pushed to a mobile device using Mobile Push Notifications (GCM or APN)?
- How do I send emojis over Ably
- Do you binary encode your messages for greater efficiency?
- Can I send messages between clients without using channels?
- Can I be notified over HTTP when a channel is created or closed?
- Are messages recovered if my connection drops?
- Am I able to check who has read published messages?
- Client-specified message ID restrictions for multiple messages published atomically
- What is Idempotent Publishing?
Subscribing and publishing
Presence
- Can I be notified over HTTP when someone enters or leaves a channel?
- Why do you have a limit on the number of members present on a channel?
- How can I implement presence subscriptions efficiently, in terms of limits?
- Can I use webhooks or other rules to maintain an external copy of the presence set of a channel or channels?
- Why don't presence members leave as soon as I close a tab?
- Can a single user be present multiple times on the same channel?
- I don't understand why I see so many presence messages in my stats.
- What happens if I exceed the number of members present on a channel?