TikTok doesn't let you upload or select custom fonts anywhere in the app, so "fancy font" text is really just ordinary Unicode letters borrowed from other character blocks — bold and italic mathematical alphabets, Gothic/Fraktur letters, circled letters, and more — that happen to look stylized while still being plain, copy-pasteable text. This tool generates every style at once from a single input so you can scan the list and grab whichever look fits your bio or caption. Because these are less common Unicode ranges, a few very old devices or minimal system fonts may render a style as a blank box instead of the intended character.
Bios and captions generally accept them fine, but some fields — like your @username — restrict input to plain alphanumeric characters and will reject or strip anything outside that set.
Each style pulls from a different, less common Unicode block, and not every font installed on every device includes glyphs for all of them — when that happens you'll see a small placeholder box instead of the intended letter.
Yes — copy the parts you like from different rows and paste them together manually; there's no restriction on mixing styles within the same piece of text.