Is there a limit for the attachment size in Messages? I'm trying to send a 36 MB .mp4 video via Messages, but I'm not exactly sure if it's working.

After sending the file, the CPU usage of the processes VTDecoderXPCService and IMTranscoderAgent goes up very high (~300%) and then only about 11 MB of data are send.

I doubt that Messages is performing some magical compression that results in &lt;30% of the original video file size for the transfer, instead I assume that the whole file is not send. But I'm not receiving a warning such as: "Could not transfer file. Attachment too large..."

Is there a limit for the attachment size in Messages?
Despite Joost's links, Apple did officially provide a size limit for Messages attachments.

Extracted from Mountain Lion's Features page:


  Send large attachments: Send high-quality photos, full HD video, or documents. iMessage allows attachments of up to 100MB.


Your 36MB file is, indeed, off the limit.