The source of this page is just a cat face:
https://nothing-to-see-here.surge.sh/
View source. You'll see (=･ω･=) and nothing else.
But the page runs. Rainbow animation, layout, everything.
The entire JavaScript is encoded as invisible Unicode
Variation Selectors attached to the cat emoji.
Unicode VS (U+FE00–FE0F and U+E0100–E01EF) map
precisely to 256 byte values. Any byte sequence can
ride inside normal text, invisible to readers,
surviving copy-paste across Slack, X, LINE, iMessage.
That's subtext.