Megaskin
Summary:
One work skin for every kind of social media in your fic: iMessage, WhatsApp, Twitter/X, Instagram, Tumblr, email and Discord, with inline translations that work in all of them. Each chapter takes one app apart, so you can use the whole thing or just the bits you need.
Notes:
This is a work in progress, and more apps will be added over time. Each app has a CSS chapter after its HTML chapter, explaining how its part of the skin works, with a link to copy just that part. The last chapter has the whole skin in one.
The examples here use the skin exactly as it is on AO3. Use the Hide Creator's Style button at the top of any chapter to see how your chats read with the skin switched off.
Want the whole skin now? Download the full megaskin CSS and paste it into a new work skin on AO3.