Upside Down Text Generator

How does an upside down text generator work?

Typing Hello world returns plɹoʍ ollǝH in two operations. The tool swaps each character for another that exists in Unicode and happens to look like the original turned over: a becomes ɐ, borrowed from the phonetic alphabet, while 4 becomes ㄣ, a Bopomofo letter from Mandarin phonetics. It then reverses the order, since a line rotated by 180 degrees ends where it began.

Substituting without reversing leaves a half-turned line that still reads left to right, the usual sign of a broken flip. The substitution table lists characters in pairs, so it runs both ways: to flip text back to normal, paste the upside down line into the same box. That round trip is the fastest check when a result looks wrong.

What is the difference between flipped text and mirrored text?

People use reverse and upside down as if they meant the same thing. Flipping rotates the line, so the character order reverses and every glyph turns into its rotated twin. Mirroring reflects it left to right, so the order reverses while the letters keep their normal shapes.

Some people call it a text generator upside down, others a reverse text generator. That second name fits the mirrored line, which reverses reading order and nothing else. Punctuation rotates too, so the sample "Why is this upside down?" comes back as ¿uʍop ǝpᴉsdn sᴉɥʇ sᴉ ʎɥM with the question mark leading the line.

Why do some upside down letters show up as empty boxes?

The box, known as tofu among typographers, appears when the reading device has no glyph for that code point, the number Unicode assigns to a character. 45 of the 134 supported characters sit outside Basic Latin, scattered across the Greek, Cyrillic, Bopomofo and mathematical blocks, where font coverage varies from one machine to the next. Capital B maps to 𐐒, a Deseret letter at U+10412, the only character in the table above U+FFFF and the first to vanish on an older system.

Instagram, X, Discord and any other field that takes Unicode accept the line, since these are ordinary text characters. The receiving app draws each glyph with the font it has, so a line that renders here may show gaps on another phone. The same font dependency hits every Unicode trick of this kind, including small text and cursive lettering. Sending a short test first is worth the ten seconds when the message matters.

Which characters can be flipped?

The table holds 134 characters. 89 come straight off a keyboard: the 26 letters in both cases, the ten digits and 27 punctuation marks counting the space. The box also accepts the other 45, the rotated shapes themselves. That is what makes the conversion back work.

Lowercase k already claims ʞ and lowercase d already claims p, so K flips to ⋊ and D flips to ᗡ rather than reuse a shape. Among digits, 6 and 9 swap while 0 and 8 read the same either way up.

Anything outside the table passes through untouched. Accented letters such as é and symbols such as % and @ stay exactly as typed. Emoji survive whole because the conversion walks code points rather than 16-bit units, so a 👋 sitting mid-sentence changes position without breaking apart.