Moments and Check-Ins are sent to people not on the app with an SMS text message from the Threads sms shortcode (5-digit number).
If you’ve selected to send a Moment or Check-In to someone not on the app, Threads will prompt you with the option to customize the text message that is sent to your recipient.
The text message, sent from the Threads 5-digit shortcode, includes your name, photo, message, and a web link to view the Moment or Check-In you sent.
When they tap on the link in the SMS, they’ll be able to view and react to your Moment or Check-In from their web browser (without downloading the app). You’ll receive this reaction in your Threads app. If they’d like to reply to your Moment or Check-In, they’ll be prompted to download the app.
Here’s an example of the text message sent:
Hey it's Adam! I sent you a Moment or Check-In. It's a new way for me to share what's going on in my life directly & privately with the people who matter - like you! I can't wait to hear about how you're doing, so send me a Moment or Check-In back on Threads.