You might have seen someone commenting on a blog or video with a unusual upside down font, and now you've come looking to see how it's done. Well, look no further, because they very likely copied and pasted upside down text from a translator just like this.
The way this translator works is very simple: Unicode is a set of standardised symbols which includes hundreds of thousands of different symbols. Most modern web browsers have implemented a large number of these so you can view them on webpages (when you can't, a generic hollow square usually appears in its place). So, within unicode there just so happen to be a set of symbols which roughly correspond to upside down versions of normal text symbols. So this app simply converts each normal text symbol to its roughly-equivalent upside down unicode character.
You might notice that a few of the upside down letters aren't actually upside down at all. For example, when you try to convert the "@" character, it stays the same. That's simply because there isn't a flipped equivalent of the "@" character. Unicode didn't intentionally create a set of upside down symols for each normal character - all of the flipped characters have just occurred by coincidence. For example, the upside down question mark: "¿" was created for languages like Spanish, which use that symbol in their normal sentences.
You should be able to copy and paste the upside down letters to most social media sites including blogs and the like. Any place that supports unicode characters will generally support all of them. You may only have trouble when trying to use the mirrored letters and characters for email addresses, URLs and that sort of thing.
There are several lists of upside down characters around the internet. The wikipedia section on upside-down text contains a fairly complete table of all the characters. Below is the full lower-case upside down alphabet for you to individually cut and paste:
z ʎ x ʍ ʌ n ʇ s ɹ b d o u ɯ l ʞ ɾ ı ɥ ɓ ɟ ǝ p ɔ q ɐ