Supported File Types and Size(s)

Learn which media formats are supported for MMS, file size limitations by carrier, and best practices for sending multimedia messages with Chekkit.

Supported File Types 

Chekkit SMS supports attachments with the following image file formats:

• JPEG/JPG
• PNG
• GIF

*These image file types are supported by our telecom provider, Twilio, and will be formatted for delivery on destination devices.

Note: Twilio accepts some additional file formats as attachments, but these file types are not compatible with Chekkit.

MMS Message Size Limitations (for non-image messages) 

For file types other than JPEG, PNG, and GIF, the total file size limit for attachments depends on the receiving carrier. Here are the attachment size limitations for MMS sent from either long code or short code numbers to the top US-based carriers:

We recommend using attachments no larger than 600KB when sending files that are not JPEG, PNG, or GIF images.

*We recommend 600KB when sending over AT&T from Long Code to avoid the potential of file resize failures occurring at the carrier partner's network. 

File Transcoding 

We will automatically transcode image file attachments in one of the supported file formats (JPEG, PNG, and GIF). We will not transcode or resize any other types of media. Images are auto-transcoded, non-images are not.

To ensure compatibility with all MMS-supported carriers, we recommend reducing the file size of any attachments with an "accepted" file type before attempting to send them.

If your media is not an image file and is larger than the limit shown above for the destination carrier, your MMS message will likely fail to send.

Number of Attachments Supported 

Chekkit supports up to 10  attachments, as long as the total size of the message body text and all attachments is less than 5 MB. An MMS message body can generally be up to 1600 characters long.

• If your message (including body text and media) is larger than 5 MB, your message request will likely fail. 

• Each MMS message, regardless of size, will always be counted as a 1-segment message.

  
  

Incoming MMS messages 

Inbound MMS to Chekkit numbers is also constrained by carrier behavior and Chekkit’s hosting rules; Chekkit does not transcode incoming media. Expect effective limits similar to outbound (and many carriers compress before Chekkit ever receives it). Chekkit does not perform any transcoding or resizing on incoming media attachments, but the handset or sending carrier will likely apply transcoding before the file reaches the dashboard.

Typically, mobile handsets will restrict the number of attachments on an MMS message, or the total size of the message; because of this, messages with more than 10 attachments are uncommon.

SMS/MMS message segments

SMS ≠ MMS.

SMS: Texts are billed in chunks called segments.

• Up to 160 normal characters (letters, numbers, spaces) = 1 segment.
• If you use emoji or special characters, the limit is 70 characters.
• Longer texts get split into multiple segments, and you’re charged for each.

MMS (with pictures/videos): billed per message, not per segment.

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If you have any other questions, please contact us at support@chekkit.io!