What should you do first when a post goes viral?
- Do not change the keyword. People are copying what earlier commenters typed. A new keyword splits them.
- Check your DM allowance. A spike can use a month's DMs in hours. If you are close, upgrade now, not after.
- Pin a comment with the keyword and "check your DMs, or Requests if you don't follow me yet".
- Leave the automation running. Pausing to edit it leaves a gap of unanswered comments.
- Answer real questions later. Comments without the keyword can wait a few hours. The automation has the requests covered.
How many DMs can Instagram send per hour?
Meta sets the limits, not your tool. These are the figures from Meta's documentation as of October 2026.
| Limit | Figure | What it means for you |
|---|---|---|
| Private replies to post and reel comments | 750 per hour per account | At most 18,000 comment DMs a day from one account |
| Time to send a private reply | 7 days from the comment | A queue has a week to work through the backlog |
| Private replies per comment | One | Each commenter gets one DM until they reply |
| Messages after the person replies | 24 hours from their reply | Follow ups only reach people who answered |
| Send API, text and links | 100 to 300 calls per second, depending on the Meta page | Rarely the bottleneck for comment DMs |
| Inbox volume | Over 72,000 messages sent and received | Meta says new messages stop showing and sending until volume drops. It does not say over what period |
Meta's pages disagree on the Send API figure: the Instagram Platform overview says 100 calls per second, while the Messenger Platform rate-limit page and a 2024 changelog entry say 300. For comment DMs, the 750 an hour private reply limit is the one you will meet first.
What do you need in place to handle the spike?
- Keyword automation on the post, ideally set up before it went live.
- Enough monthly DMs. ReplyRep plans run from 2,000 on Free to 400,000 on MAX.
- A queue for anything over Meta's limit. The Excess DM Queue holds overflow in order instead of dropping it, on Lite and up.
- A way to recover anything missed. SendBack goes back for interactions that were skipped or delayed, on Lite and up.
How do you handle a viral post with ReplyRep?
- 1
Check usage and upgrade if needed
Open the dashboard and compare DMs used with your plan. Lite has 10,000 a month, Boost 40,000, MAX 400,000.
- 2
Confirm the queue is on
On Lite and up, the Excess DM Queue holds anything over Meta's sending limit and drains it in order, as fast as Meta allows.
- 3
Turn on the public reply
A varied public reply (Lite and up) tells the thread the DMs are going out, which stops people commenting "didn't get it" ten times.
- 4
Add a Global Trigger for the questions
Viral posts bring the same three questions: price, shipping, where to buy. A Global Trigger answers them anywhere, including DMs from people who skip the comments.
- 5
Let SendBack catch what was missed
As the spike eases, SendBack goes back for anything skipped or delayed, inside Meta's 7-day window.
- 6
Work the replies
People who answered the DM have opened a 24-hour window. Answer them, or let a follow up or AI reply handle the common ones.
Worked example: 12,000 comments overnight
A reel posted at 9pm gets 12,000 keyword comments by 5am. Here is how Meta's limits play out.
- At 750 private replies an hour, sending all 12,000 takes 16 hours. By 5am, 6,000 have gone out and 6,000 are waiting.
- Everything is answered by about 1pm the next day, well inside Meta's 7-day window.
- On the Free plan, the 2,000 monthly DMs would run out in under three hours of sending. On Boost, with 40,000, the whole spike fits with room left.
- Without a queue, sends over the limit can fail, and those people never get the DM they asked for.
Public reply
Sent, it's in your DMs (check Requests if you don't follow yet)
DM
Hey {first_name}, sorry for the wait, it's been a busy night. Here it is: {link} Anything else you want to know? Just reply.
The DM admits the delay, which is honest when the queue runs for hours, and ends with a question so replies open a conversation.
Be ready before the next one
The Excess DM Queue and SendBack are on Lite and up. Set them up now, not at 3am.
Why are commenters saying they did not get the DM?
- It is still in the queue. At 750 an hour, a big backlog takes hours. They will get it.
- It is in Requests. Viral posts reach non-followers, and Meta delivers their private replies to Requests.
- They mistyped the keyword. Spikes bring every spelling. Check a sample of comments that did not fire.
- The allowance ran out. Upgrade, then use SendBack for what was missed. Meta's 7-day window still applies.
- They commented twice. Each comment gets one private reply. Their first DM has it.
What should you do in the 48 hours after the spike?
- 1
Answer the people who replied
Everyone who answered your DM has a 24-hour window open. Reply to questions first: these are the warmest leads you will get from the spike.
- 2
Read the comments that did not fire
Look for common misspellings or alternative words, and add them as keywords so late commenters are caught.
- 3
Clear the non-keyword questions
Answer the specific questions in the thread by hand. Answers posted under a busy reel are read by thousands.
- 4
Check the numbers
Comments, DMs sent, clicks and sales from the campaign's UTM tags. This tells you what the spike was worth.
- 5
Post the follow-up content
New followers arrived for one post. Give them a second reason to stay within a day or two, with automation set up before it goes live.
How do you prepare for the next viral post?
- Set automation on every post before publishing. You never know which one will travel.
- Size your plan for your busiest month, not your average one.
- Write the DM to stand alone, so a stranger understands it without context.
- Keep a Global Trigger for the questions strangers ask.
- Read Instagram DM limits for every limit in one place, and will auto DM get my Instagram banned for the policy side.