As my wife, friends, and work colleagues can attest to, I often communicate using GIFs (hard G, don't @ me). Most of my usage is within Slack, though I do occasionally use them in iMessage. However, my experience with iMessage and GIFs has been problematic. Whenever I'd send someone a GIF via iMessage, the recipient would often reply saying it was unwatchable because the size of it was so small.
It didn't matter where the GIF came from (either pasted in or sourced from an iMessage app like GIPHY), the resolution of the GIF received was always extremely low. I had no idea what was causing this and just assumed it was an issue with iMessage's handling of GIFs. But after receiving watchable GIFs from friends, I began to investigate the issue.
I took a look at some settings for Messages and noticed that there is a Low Quality Image Mode option that was enabled. I remember enabling this option several iPhones ago to save bandwidth whenever I sent photos via iMessage, back when I was on a terrible data plan in the UK. After turning this option off, GIFs were untouched when sent and were received as intended—in their full, bloated glory.
To everyone in my iMessage conversations, I apologize in advance for the upcoming impact to your data plans.