Instagram doesn't actually let you change the font
Instagram's bio and caption fields render in a single sans-serif
typeface - the system UI font on whatever device the viewer is
holding. There's no font picker, no markdown for italics, no
<strong> tag. So how do you see accounts running headlines in
bold, italic, script, or ššÆššØš±š²šÆ? They're not
using a font. They're using Unicode.
The trick: alternative letterforms in Unicode
Unicode is the table of every character that computer text can represent. It includes the regular Latin alphabet (A, B, Cā¦) but also dozens of alternative alphabets that look like styled Latin letters. The "Mathematical Alphanumeric Symbols" block, for instance, contains a complete bold A-Z, italic A-Z, sans-serif A-Z, script A-Z, and so on - each one a real, individually-encoded character. Copy a character from that block and paste it into Instagram, and Instagram displays whatever your device's font has for that code point. On most devices, the bold mathematical letter "š" looks genuinely bold.
This tool maps the regular alphabet to one of 16 such Unicode blocks and lets you copy the result. The output is a string of plain Unicode characters - no font files, no images, no special markup - which means it survives the paste into any text input that accepts text.