Anywhere text is accepted: Instagram bios, TikTok names, Discord, WhatsApp, gaming profiles and documents. The full Tiny Caps alphabet is linked above.
What is the Tiny Caps letter D?
It is the letter D rendered as the Unicode character ᵈ (code point U+1D48), part of the Tiny Caps styled alphabet. It is a single character you can copy and paste anywhere.
How do I type ᵈ on my phone or computer?
You do not type it from a keyboard; you copy it. Press the copy button above and paste it into any app. That is the whole point of Unicode styled letters.