Send DMs that actually deliver

A DM only goes out if Instagram's messaging rules allow it. Miss those rules and the reply is silently dropped, so they're worth two minutes of your time.

What a DM action can contain

A send-DM action can be any of these message formats:

Text — a plain message with your link or call to action.
Card — an image with a title, subtitle, and one or more buttons.
Carousel — a swipeable row of cards.
Quick replies — a text message with tappable chips the person can pick from.

Buttons and quick-reply chips can either open a URL or advance the automation to a different step (so a tapped button can branch the flow). A DM action can also attach media you've uploaded to Files — note that a text caption plus an attachment arrives as two messages, the text first and the file right behind it.

A DM action runs as a reply triggered by a comment, or as a reply to an incoming DM. Keep it conversational — you're answering someone who just raised their hand.

The "sent with big." credit

Automation DMs end with a short signature — a blank line, a rule, then one line:

—
sent with big. → https://itsjustbig.com/?ref=dm

It's added once per conversation, not once per message. The first DM in a run that carries text gets it; every later message in that same conversation goes out without it.
Some messages never carry it. Public comment replies (the threaded comment under your post), card, carousel, and quick-reply messages, and a media-only message with no text are all left alone.
Your message is never shortened to make room. If adding the credit would push the message past Instagram's per-message length limit, the credit is dropped and your text goes out whole.
The builder shows you exactly what sends. The message preview renders the credit inline in the bubble as you write, and tells you when a message is too long to fit it.

The credit is on by default on every plan. On teeny (free) it can't be removed. Every paid plan (tiny and up) can turn it off under Settings → Billing — it stays on until someone does, and changing it needs an admin role or higher. See Plans.

The rule that decides delivery: the messaging window

Instagram only lets you send a DM inside an open messaging window:

Comment-triggered DMs can be sent within 7 days of the person's comment.
DM conversations open a 24-hour window that re-anchors each time the person messages you again. As long as they keep replying, the window keeps reopening.
Once the window has expired, the send can't go out and the automation run is marked expired — big won't keep retrying against a closed window.

The full timing picture is on The 24-hour window.

Why a DM might not send

The messaging window has closed (most common).
The recipient's account can't receive automated messages.
You've hit your plan's weekly sending cap, which blocks new conversations from starting (ones already mid-flow finish) — see Limits & plans.
Your workspace has been suspended, which pauses new automation runs and holds queued sends until it is lifted.

If a send didn't happen, "Why didn't my automation fire?" walks through each cause.

Next step

Read The 24-hour window so your replies always land inside an open window.