SMS carriers and have attachment file size limitations to prevent deliverability issues and to make sure that their servers are not overloaded with hefty file sizes while millions of people around the world use their services to send SMS.
SMS
We support up to 10 attachments, as long as the total size of the message body text and all attachments is less than 5 MB.
Carriers also have limits. The average is 300kb-600kb and can go up to 3.5MB for tier 1 providers (AT&T/Verizon, etc.)
Here are the Carrier Attachment Size limits for some common US Carriers:
The file sizes above will generally be passed along to the wireless carriers. However, due to differences in handsets, file types, and transcoding, we recommend you send attachments no larger than 500KB to ensure the best chance of delivery.
These image file types are supported:
jpeg
png
gif
As of May 2021, there is an issue with Toll-Free MMS file size support; for these numbers, you must ensure that any attachments (including images) are 600kb or smaller.