Make bold text for places that have no bold button: Instagram captions, TikTok bios, LinkedIn posts, X. Tap a style to copy it.
Before you paste it into your name. Because these are different characters, not a font, a screen reader may read each one by its official name (“mathematical bold capital H”), letter by letter, or skip it, and search inside apps usually won’t match it, so people typing your name may not find you. Keep your name, @handle and anything important in plain text, and use styles for decoration. Tap the magnifier on any style to see exactly which characters you’d be pasting.
Sans-serif bold looks closest to the bold you'd see in an app and is the easiest to read, which makes it the usual choice for a heading in a caption or post. Serif bold looks more like a printed book. Both include bold numbers. There are also bold italic, bold script and bold gothic versions.
Use bold for a few words, not whole paragraphs. Each bold letter is a separate Unicode symbol, so a screen reader may read it oddly, and the words won't be found by search in most apps. On LinkedIn and X that means a bolded keyword won't match a search for that keyword.
Apps that support formatting have real bold, which is better. In Discord, WhatsApp and Slack, wrap text in asterisks instead (**bold** in Discord, *bold* in WhatsApp and Slack).