Upside down text generator

Two steps, not one

Flipping text properly takes two operations. First every character is replaced with a Unicode look-alike that appears rotated 180 degrees. Then the whole string is reversed, so that when the page is physically turned over the words read left to right again.

hello
step 1 (substitute):  ɥǝllo
step 2 (reverse):     ollǝɥ

Skip the second step and you get characters that look upside down but read backwards, which is the giveaway of a lazy implementation.

Where the rotated characters come from

There is no “upside-down alphabet” in Unicode. The characters are borrowed from wherever a suitable shape happens to exist — mostly the International Phonetic Alphabet, plus a few from Latin extensions, Greek, Cyrillic and even Deseret:

The letters that will not flip

Some are symmetrical and need no substitute — o, x, z, H, I, N, O, S, X, Z. Others have no rotated form anywhere in Unicode; capital Q and G are the usual casualties and simply pass through as themselves. That is a limitation of the character set, not of the tool.

Punctuation flips too

Full stops rise to the top of the line, commas become apostrophes, and question and exclamation marks turn into their inverted Spanish forms ¿ and ¡ — which is what those characters were designed for in the first place. Brackets and braces swap direction so that a pair still encloses the right text after reversal.

Flipped versus reversed versus mirrored

• Flipped — substituted and reversed; reads correctly when you rotate the screen.
• Reversed — the same characters in the opposite order, nothing substituted. Useful for palindrome checking.
• Mirrored — a true left-right mirror needs different glyph shapes again, and Unicode has far fewer of those, so genuine mirror text is normally done with CSS rather than characters.

The first two are both available above so you can compare them directly.

Support

Better than you might expect, because IPA characters are in almost every system font. The Deseret capital B is the weak point — it is outside the Basic Multilingual Plane and shows as a box on some older Android builds. Everything else renders on any current phone or desktop.