Automated DMs work within a few hard limits set by Meta and a few soft limits set by human attention. Knowing both stops you writing a message that gets cut off or ignored.
Message length
Meta's messaging API accepts text messages up to 1,000 characters. Message templates with buttons have tighter limits on the text above the buttons. To stay safely inside every case, DM Flow limits each automated message to 640 characters.
The practical limit is shorter. On a phone, 640 characters is a wall of text. Aim for 150 to 300: two to four short lines.
Button labels
Buttons have short labels. DM Flow allows 20 characters per button, which fits labels like "See all colours" or "Book my slot". Longer labels get cut off on some phones.
Number of messages
This is the limit that shapes automation most:
| Situation | What you can send |
|---|---|
| Someone commented, nothing else | One private reply to that comment, within 7 days |
| They replied or tapped a button | Messages within 24 hours of their last message |
| More than 24 hours since their last message | Nothing automated |
So the first message must be complete or must invite a tap. See Instagram private replies explained and the 24-hour window.
Links
- Links must be full addresses starting with
https:// - A link behind a button looks cleaner than a raw URL
- Some link shorteners are flagged as spam; use your own domain where you can
Hourly sending
Meta limits how many messages an account can send per hour, which matters on viral posts. See Instagram DM limits per hour.
Writing within the limits
A good structure that fits easily:
Hi {name}! [What you're sending.] [One useful detail.]
[Button: what happens next]
Example:
Hi {name}! Here's the bridal lehenga lookbook. Custom sizing takes 3 weeks, so do message us early for wedding dates.
[Open lookbook]
That is under 200 characters.
Frequently asked questions
Can I send images in automated DMs?
The API supports images and other attachments. Comment-to-DM tools usually focus on text and buttons because they load fastest.
Can I use line breaks?
Yes. Short lines are easier to read on phones.
Do emojis count as characters?
Yes, and some emojis count as two.
Is there a limit on keywords?
That is a tool limit, not Meta's. DM Flow allows up to 20 per automation.