How long can a business reply to an Instagram message?

The rule, from Meta’s own pages

Meta states the rule in its Instagram messaging documentation and in its Messenger Platform and IG Messaging API policy. Both are written for apps that send through the API, so a tool built on the API works inside them. This is what the pages said on 27 October 2026.

The size limits for what you send inside the window, from the Send Messages page:

Meta’s overview page also sets the speed: 100 calls a second per Instagram professional account for messages with text, links, reactions and stickers, and 10 calls a second for audio or video.

What opens the window

The pages do not describe the opening actions in the same way. The Instagram Login page says conversations begin when a person sends the account a message. The Send a message page of the Messenger Platform, which also covers Instagram professional accounts, lists more actions that open a standard window:

• a message to your Instagram professional account;
• a tap on a call-to-action button inside a conversation;
• a first message after a Click-to-Direct ad, where the window may last up to 7 days;
• a tap on an ig.me link that leads to an existing conversation;
• a reaction to a message;
• a comment on a post of the account.

A comment is on that list, yet the private-replies page limits an account to one message to a commenter until that person answers. The stricter page is the safe one to plan around: after a comment, one message; after a message, 24 hours. The comment case has its own answer.

Meta’s pages do not use the word “renew”. Each new message from the person is an action in the list, and Mellow Hub counts from the person’s latest message to the account.

What happens after the 24 hours

The window closes and an app can no longer send ordinary messages. Meta’s pages describe three things that remain, and none is a way to keep marketing to the person:

• A human agent’s reply. Meta’s overview says the Human Agent feature lets a person respond with the human_agent tag within 7 days of the user’s message, for cases where a user’s issue cannot be resolved in the standard window, such as a business that is closed for the weekend or an issue that needs more than 24 hours. It is listed among the features and permissions the API uses, and the Send Messages page asks for a custom inbox for human-only experiences.
• Tagged updates. The policy page describes message tags as important, personally relevant one-to-one updates outside the window, for a set of approved use cases. They may not carry deals, offers, coupons or discounts. Using a tag outside an approved case may restrict the account’s ability to send messages, and some tags exist only on the Messenger Platform, not for Instagram. The Send a message page carries a dated notice: since 27 April 2026, requests with the tags CONFIRMED_EVENT_UPDATE, ACCOUNT_UPDATE and POST_PURCHASE_UPDATE get error code 100.
• The person writes again. A new message from them opens a new window.

Three other routes that the policy page describes for Messenger are not available for Instagram: one-time notifications, news messaging and sponsored messages. Meta’s pages say an app has the duration of the window to send, and they do not say what the API returns for a message sent after it, or whether there is any grace. This page states neither.

What is not allowed

• Starting a conversation. The Messenger Platform page says that to send a message to a person on Messenger or Instagram, the conversation must be initiated by that person. The one documented exception is the private reply to a comment.
• Broadcasting. The pages we read describe no way to send one message to a list of people who have not written to the account. Group messaging is not supported: an Instagram professional account converses with one customer per conversation.
• Promotions outside the window. Tagged messages may not be promotional.
• Hiding that it is automated. When applicable law requires it, an automated chat has to say that the person is dealing with an automated service: at the start of a conversation, after a significant lapse of time, and when a chat moves from a person to automation. Meta names California and German users and recommends saying it even where it is not required.
• Messages that break the Community Standards. Meta’s Help Center says these can lead to temporary restrictions on sending messages and, after repeated warnings or for a severe violation, to the Instagram account being disabled.

People can block or mute a conversation with a business at any time, and Instagram’s Help Center tells them how to stop an automated chat.

Start with Instagram’s and Meta’s own tools

• Frequently asked questions. For business and creator accounts. In the app, open Messages, then Tools, then Frequently asked questions, and add up to four questions, each with an optional automated response. If someone picks one, their message goes to your Requests and you accept the request to reply.
• Inbox automations in Meta Business Suite. For Instagram business accounts connected to Business Suite. The templates include a greeting for a first message, an away message, frequently asked questions, location, contact information and hours. Custom keyword automations are desktop only: up to five keywords or phrases per automation, case-sensitive, matched exactly, and sent after 15 minutes unless you answer in person first.
• Regions. Meta’s set-up page says some organic messaging features for businesses, and ads delivered to and from Europe and Japan, are unavailable. Check that a template is offered for your account before relying on it.

How Mellow Hub applies the 24 hours

Hub is one way to automate answers, and Meta’s tools above come first. How to set up a keyword rule is in Mellow Hub’s Instagram comment-to-DM guide; the 24-hour rules on this page are the ones it works within. It sends through Instagram’s official API on Mellow’s own Meta app, which has passed Meta’s App Review for the permissions involved. Meta approved instagram_business_manage_messages with Advanced access on 26 October 2026, which is the level its Send Messages page requires for accounts a developer does not own, and replies to direct messages by keyword are open to every Hub profile.

Keyword answers. In Hub’s Auto-replies screen you connect an Instagram professional account through Instagram’s own sign-in and add a rule with Direct messages as the source. A rule has words to listen for and several answers, and Hub picks one at random. When a person sends a message that contains one of the words as a word of its own, in any letter case, Hub replies in that conversation. Because the rule answers a message that has just arrived, the reply is always inside the window. The same person gets at most one automatic answer from the same rule an hour, however often they repeat the word. Hub never answers the account’s own messages, deleted messages or messages without text.

Agents. An AI agent connected through MCP can use list_messages, which lists recent conversations and, where the person wrote last, until when the account may answer: 24 hours after their message. reply_to_message sends one message to one person. It first checks that the person wrote last within the past 24 hours, and if not it refuses with message_window_closed and sends nothing; if Hub cannot read the conversation list, it leaves the decision to Instagram. Only an autopilot key can send, within its daily ceiling, and a key in review mode only reads.

Where Hub sends an Instagram message. In four situations only: a comment rule’s private message, a keyword answer in a direct message, an agent’s reply to a comment, and an agent’s reply to a message. Each answers something the person did first. Hub has no broadcast, no list of recipients, no scheduled direct messages and no follow-up after the window, and it does not use the Human Agent tag.

The first 3 posts are free, however many networks each one goes to, and need no card. After that Hub is paid: plans start at $19 a month (Solo), after a 7-day trial with a card on file that costs nothing if you cancel before it ends, and a monthly plan's first month is 20% off. Publishing is unlimited on every plan, under a fair-use ceiling that stops automated floods (900 publications a month on Solo), where one publication is one post on one account, so a post sent to five networks counts as five toward it. There are no automatic overage charges.