How long can you send a private reply to an Instagram comment?

The rules, from Meta’s own pages

A private reply is a direct message sent in answer to a comment. Meta describes it in its Instagram developer documentation, which is written for apps that send through the official API, so any tool built on that API works inside the same limits. These are the rules as the pages read on 27 October 2026.

Bytes are not characters. A message in Cyrillic, or one with emoji, reaches 1,000 bytes at fewer than 1,000 characters.

What “one reply per comment” means

Meta’s wording is that only one message can be sent to the commenter. The request that sends the reply names a comment, so the natural reading is one private reply per comment, and nothing more until the person writes back. The pages do not say whether Meta would accept a second private reply to a different comment from the same person, and we have not tested it. Mellow Hub answers each comment once and never sends a second message to it.

The private reply is also the documented exception to a stricter rule. Meta’s Messenger Platform page says that to message a person on Messenger or Instagram, the conversation must be initiated by that person, and the Instagram Login page says an app can message a person only after that person has messaged the account. A comment lets you open the conversation yourself, once. The next step belongs to the person: if they answer, the 24-hour messaging window opens.

What you can do after the 7 days

The private route closes for that comment. Meta’s pages say the reply must be sent within the 7 days; they do not describe what the API answers once the time has passed, so this page states no error message. What remains is not a private reply:

• Reply under the comment. A public reply is a different action. In the app, open the post, choose Reply below the comment, write it and post it. Instagram’s Help Center says that mentioning the person notifies them.
• Invite them to message you. Say so in the public reply. If they send your account a message, you have 24 hours to answer it.
• Leave it. Not every comment needs an answer.

Start with Instagram’s and Meta’s own tools

For a handful of comments, answer by hand. A public reply needs nothing but the Instagram app, and the Help Center pages we read describe replying under a comment; none of them describes a private reply button.

For comments that contain a keyword, Meta Business Suite has its own automation. On desktop, open Inbox, then Automations, choose Create automation, pick the Comment to message template and follow the on-screen instructions. Meta’s set-up page describes it as sending a message reply to comments on your posts that contain specific keywords or phrases, and its overview page says the template is available only on desktop. Three cautions from those two pages:

• The overview words the same template as a reply to comments that contain specific hashtags, so open the template to see what it matches.
• Depending on the channels you have connected, some templates may not be offered to you.
• The set-up page notes that some organic messaging features for businesses, and ads delivered to and from Europe and Japan, are unavailable.

Neither page says how long after a comment the automation can still send. The 7 days above is the limit to plan around.

Tools built on the API

A tool that sends through Meta’s API for Instagram works inside the limits in the table: 7 days, one message, a reply to the commenter only. If a tool promises to message commenters after a longer time, or to send each of them several messages, ask which API it uses and compare its answer with Meta’s page. One permission detail is worth knowing. Meta’s page lists instagram_business_basic and instagram_business_manage_comments for the Instagram Login route, but on 10 October 2026 our own test with exactly those two permissions was refused by Meta with error 10, and the same rule sent the message once the account had also granted instagram_business_manage_messages and had Instagram’s “Allow access to messages” setting switched on. That is one observation on one account, with two changes made together, not a rule from Meta.

How Mellow Hub applies the 7 days

Hub is one way to automate these rules, for people who want them next to their scheduling and for AI agents. The step-by-step setup of a comment rule is in Mellow Hub’s Instagram comment-to-DM guide; the rules above 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, and comment-to-message replies are open to every Hub profile. You connect an Instagram professional account in Hub’s Auto-replies screen through Instagram’s own sign-in, then add a rule. A rule has three parts:

• Words to listen for. A comment matches when it contains one of them as a word of its own, in any letter case. The word guide matches “GUIDE please” and “send the guide”, but not “guidelines”. Emoji and other symbols match where they stand.
• A public reply, optional. You write several variants and Hub picks one at random for each comment.
• A private message, optional. This is the one private reply Meta allows.

A rule listens on every post of the account or on one post, and it needs a public reply, a private message, or both. For each comment Hub does the following:

• It answers the comment once. If two rules match, a rule for one post is tried before a rule for every post, and the first match answers.
• It skips the account’s own comments, replies inside a thread, and comments on a live broadcast, because Hub subscribes to the comments feed and not to live comments.
• It sends the private message only when the connected account granted the messaging permission. Without it, only the public reply goes out.
• It spaces answers out. After a run of comments, the rest wait in a queue and go out one at a time, with pauses, instead of all at once.
• It lists every answer on the Auto-replies screen and writes it to the audit log. You can switch a rule off or delete it at any time.

Comments from before the rule. If a comment arrived before you made the rule, Hub’s catch-up lists the ones a rule would have answered that are still inside the 7 days. It stops a little short of the limit, so Meta is not asked on the last minutes. Reply to all, then Send now, queues them oldest first, because their window closes first, and Hub sends one at a time, minutes apart. Sending is yours: a signed-in person, or an agent key on autopilot, can send; a key in review mode can only preview.

Agents. An AI agent connected to Hub through MCP can use list_comments, which shows for each comment until when a private reply is open (the comment’s time plus 7 days), and reply_to_comment, which refuses a comment that a rule, the catch-up or an earlier reply has already answered. Only an autopilot key can send, within its daily ceiling. A key can also create a rule with create_autoreply: it is live at once under autopilot, and under review it is saved switched off for a person to turn on.

What Hub does not do. It does not message people who did not comment or write to the account, does not send a second message to a comment, does not broadcast to a list, and does not answer comments on a live broadcast.

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.