24-Hour Messaging Window

The 24-Hour Messaging Window is Meta's default reply window for Messenger and Instagram Direct. Once a user sends a message to a business account, the business can send standard messages back for the next 24 hours. After that, the channel closes — outgoing messages return error code 10 ("message outside allowed window") unless you attach a permitted message tag or use a paid one-time-notification.

The clock resets on every user-initiated message, not on business replies. If a user pings at 14:00 Monday, the window expires 14:00 Tuesday; if they reply again at 13:55 Tuesday, you get a fresh 24 hours from that timestamp. Echoes from your own account do not extend the window.

Why it matters

Most automation flows collapse on the 24-hour edge because the worker treats "send a DM" as a stateless operation. In practice, every send needs a window-aware gate: is this thread inside 24 hours of the last inbound? If not, escalate to a Human Agent tag (which buys 7 days, manual-only), a message tag like POST_PURCHASE_UPDATE or ACCOUNT_UPDATE, or — for paid re-engagement — a Sponsored Message campaign.

How it interacts with comment automation

The 24-hour window is a different rule set from the Private Reply Window. The private reply window covers the first DM you send to a commenter (seven days from the comment). Once the user replies inside the DM thread, you transition onto the 24-hour window and stay there.

Gotchas

• Story mentions and replies count as user-initiated messages, so they open a 24-hour window even though no DM was typed.
• Promotional content is never permitted via message tags, even inside the 24-hour window if the tag does not match the message intent.
• The window applies per page-user pair, not per app — switching automation tools does not reset it.

For tier-aware sending caps once a thread is open, see Messaging Tier.