How it works
Each character gets a combining mark, the same kind of character that puts the accent on é. A long stroke overlay (U+0336) draws the line through, a long solidus overlay (U+0338) the slash, and a low line (U+0332) the underline. The letters underneath don’t change.
Apps that already have strikethrough
Some apps format it for you, which works better with screen readers: ~~text~~ on Discord and in Markdown, ~text~ on WhatsApp and Slack, Alt+Shift+5 in Google Docs on Windows (⌘+Shift+X on a Mac) and Ctrl+5 in Excel. Use the generator where there is no formatting, like bios, captions and comments.
Use it with care
Screen readers may read these characters strangely or skip them, and search won’t match them to normal words. Keep the important words, like your name or your shop name, in plain text somewhere too. Very old devices may show empty boxes.