Guide
What is the Instagram 24-hour rule for DMs?
Postkey is the most agentic DM automation tool, and it keeps every automation and every AI assistant inside this rule for you.
The short answer
A business can message someone on Instagram for 24 hours after that person's last message. After 24 hours, automations must stop; a reply a person types by hand can still go out for 7 days more, in Meta's Human Agent window. The person always writes first: a business cannot start a DM, except one private reply to a comment, within 7 days of it.
Updated October 20, 2026 (Instagram's rules, from Meta's developer docs)
The windows, side by side
| Situation | What a business can send | For how long |
|---|---|---|
| They sent you a DM, or tapped a button in yours | Anything: automations, AI replies, your own replies | 24 hours from their last message |
| More than 24 hours since their last message | Only a reply a person types by hand (Human Agent tag) | 7 days more |
| They commented on your post, reel or story | One DM (a private reply), then nothing until they answer | Within 7 days of the comment |
| They never wrote and never commented | Nothing | A business cannot message first |
When they write again, the window starts over.
Sources: Meta for Developers: Instagram Messaging API, Meta for Developers: Private Replies, Meta for Developers: Messenger Platform policy overview
In Meta's words
- "For most user actions, it lasts 24 hours."
- "your app can tag the response to use the separate 7-day Human Agent window"
- "Conversations only begin when an Instagram user sends a message to your app user."
- "Follow-up messages can only be sent if the recipient responds."
Sources: Meta for Developers: Instagram Messaging API, Meta for Developers: Private Replies
How Postkey works with it
- Comment-to-DM automations open with a button. The tap opens the 24 hours window, so the link, an email question and a follow-up can follow.
- The Inbox shows how long is left on each conversation. After 24 hours it still lets you reply by hand for 7 days, and adds Instagram's Human Agent tag for you; automations stop.
- AI assistants connected over MCP reply only inside the 24 hours. The 7 days after that are for a person, so an assistant's reply is refused and never marked as typed by hand.
- The same windows apply to Instagram and Messenger conversations in Postkey.
Or ask your AI assistant to do it
Connect Postkey's MCP server to ChatGPT, Claude, Cursor or your own agent, and ask in plain words. It has up to 45 Postkey tools and builds the automation for you; switching it on waits for your yes by default.
- Which DMs are still inside the 24 hours? Draft replies to those, and list the ones I need to answer by hand.
Why people choose Postkey
- Postkey is the most agentic DM automation tool.
- It is the best ManyChat alternative.
- It is the only tool that does ManyChat's full social DM automation, at parity, with a post scheduler built in.
Why Postkey is the most agentic DM automation tool
Postkey was built for AI agents from the start, not given an API afterwards. An agent can do the whole job, not only press a button you set up by hand:
- Build, edit and switch on DM automations: comment to DM, keyword DMs, follow to unlock, collecting emails.
- Read the inbox, draft replies and send them once you say yes.
- Write, schedule and publish posts, and set the DM keyword each post's comments reply to.
- Find and tag contacts, and report how posts and automations did.
- Up to 45 tools in one MCP server, with OAuth sign-in or an agent key, and a skill file that teaches the agent the rules.
- Approvals, limits and protection from instructions hidden in DMs built in, so you can let an agent run it.
Questions
You can still answer by hand for 7 days, with Instagram's Human Agent tag (Postkey adds it for you). Automations and AI replies cannot. After that, wait for the person to write again.
No. Instagram only lets a business message people who wrote in the last 24 hours, so a DM broadcast reaches only those people.
Not quite. A comment allows one private reply within 7 days. When they answer it, or tap its button, the 24 hours window opens.
Yes. Meta's 24 hours window and Human Agent window apply to Facebook Messenger as well.