aestheticsymbols
Use in a combo

Outlined Greek cross copy & paste

✙ is outlined greek cross, a plain-text Unicode symbol from the Dingbats block. On Aesthetic Symbols it lives in the charms & marks collection, tagged cross. As plain text it takes on the font and colour of wherever you paste it — a bio, a username, a caption or a stream title.

Unicode
U+2719
HTML entity
✙
CSS content
\2719
JavaScript
\u{2719}
UTF-8 bytes
E2 9C 99
Made of

U+2719 ✙ · Dingbats

Will it show up? · Long-established text symbols

Plain-text characters from blocks that mainstream desktop and mobile fonts have covered for years. These are the safe ones.

Worked out from how each character is encoded, not from a test on a real device.