How does uʍop-ǝpᴉsdn text work?

Here's a website I found that will produce upside down versions of any English text.

how does it work? does unicode have upside down chars? Or what?

How can I write my own text flipping function?

how does it work? does unicode have upside down chars?

Unicode does have upside-down characters. They have "TURNED" in their name:

ƍ U+018D LATIN SMALL LETTER TURNED DELTA
Ɯ U+019C LATIN CAPITAL LETTER TURNED M
ǝ U+01DD LATIN SMALL LETTER TURNED E
Ʌ U+0245 LATIN CAPITAL LETTER TURNED V
ɐ U+0250 LATIN SMALL LETTER TURNED A
ɒ U+0252 LATIN SMALL LETTER TURNED ALPHA
ɥ U+0265 LATIN SMALL LETTER TURNED H
ɯ U+026F LATIN SMALL LETTER TURNED M
ɰ U+0270 LATIN SMALL LETTER TURNED M WITH LONG LEG
ɹ U+0279 LATIN SMALL LETTER TURNED R
ɺ U+027A LATIN SMALL LETTER TURNED R WITH LONG LEG
ɻ U+027B LATIN SMALL LETTER TURNED R WITH HOOK
ʇ U+0287 LATIN SMALL LETTER TURNED T
ʌ U+028C LATIN SMALL LETTER TURNED V
ʍ U+028D LATIN SMALL LETTER TURNED W
ʎ U+028E LATIN SMALL LETTER TURNED Y
ʞ U+029E LATIN SMALL LETTER TURNED K
ʮ U+02AE LATIN SMALL LETTER TURNED H WITH FISHHOOK
ʯ U+02AF LATIN SMALL LETTER TURNED H WITH FISHHOOK AND TAIL
ʴ U+02B4 MODIFIER LETTER SMALL TURNED R
ʵ U+02B5 MODIFIER LETTER SMALL TURNED R WITH HOOK
ʻ U+02BB MODIFIER LETTER TURNED COMMA
̒ U+0312 COMBINING TURNED COMMA ABOVE
ჹ U+10F9 GEORGIAN LETTER TURNED GAN
ᴂ U+1D02 LATIN SMALL LETTER TURNED AE
ᴈ U+1D08 LATIN SMALL LETTER TURNED OPEN E
ᴉ U+1D09 LATIN SMALL LETTER TURNED I
ᴔ U+1D14 LATIN SMALL LETTER TURNED OE
ᴚ U+1D1A LATIN LETTER SMALL CAPITAL TURNED R
ᴟ U+1D1F LATIN SMALL LETTER SIDEWAYS TURNED M
ᵄ U+1D44 MODIFIER LETTER SMALL TURNED A
ᵆ U+1D46 MODIFIER LETTER SMALL TURNED AE
ᵌ U+1D4C MODIFIER LETTER SMALL TURNED OPEN E
ᵎ U+1D4E MODIFIER LETTER SMALL TURNED I
ᵚ U+1D5A MODIFIER LETTER SMALL TURNED M
ᵷ U+1D77 LATIN SMALL LETTER TURNED G
ᶛ U+1D9B MODIFIER LETTER SMALL TURNED ALPHA
ᶣ U+1DA3 MODIFIER LETTER SMALL TURNED H
ᶭ U+1DAD MODIFIER LETTER SMALL TURNED M WITH LONG LEG
ᶺ U+1DBA MODIFIER LETTER SMALL TURNED V
℩ U+2129 TURNED GREEK SMALL LETTER IOTA
Ⅎ U+2132 TURNED CAPITAL F
⅁ U+2141 TURNED SANS-SERIF CAPITAL G
⅂ U+2142 TURNED SANS-SERIF CAPITAL L
⅄ U+2144 TURNED SANS-SERIF CAPITAL Y
⅋ U+214B TURNED AMPERSAND
ⅎ U+214E TURNED SMALL F
⌙ U+2319 TURNED NOT SIGN
❛ U+275B HEAVY SINGLE TURNED COMMA QUOTATION MARK ORNAMENT
❝ U+275D HEAVY DOUBLE TURNED COMMA QUOTATION MARK ORNAMENT
⦢ U+29A2 TURNED ANGLE
Ɐ U+2C6F LATIN CAPITAL LETTER TURNED A
ⱹ U+2C79 LATIN SMALL LETTER TURNED R WITH TAIL
ⱻ U+2C7B LATIN LETTER SMALL CAPITAL TURNED E
Ꝿ U+A77E LATIN CAPITAL LETTER TURNED INSULAR G
ꝿ U+A77F LATIN SMALL LETTER TURNED INSULAR G
Ꞁ U+A780 LATIN CAPITAL LETTER TURNED L
ꞁ U+A781 LATIN SMALL LETTER TURNED L

However, it's far from a complete set. Most upside-down text works by choosing characters that happen to have a close-enough resemblance to upside-down letters. It's the equivalent of typing 0.7734 on your calculator to spell "hELLO".

does unicode have upside down chars?

Yup! Or at least characters that look like they are upside down. Also, regular English-alphabetical characters can appear to be upside down. Like u could be an upside-down n.

To code it up, you just have to take an array of characters, display them in reverse order and replace those characters with the upside down version of them. This will get you a good start: zʎxʍʌnʇsɹbdouɯןʞſıɥbɟǝpɔqɐ

When 'uʍop-ǝpısdn' is copied and echoed into a hex dump program, the string is seen as:

75 CA 8D 6F 70 2D C7 9D 70 C4 B1 73 64 6E

The UTF-8 breakdown of that is:

0x75      = U+0075 = LATIN SMALL LETTER U
0xCA 0x8D = U+028D = LATIN SMALL LETTER TURNED W
0x6F      = U+006F = LATIN SMALL LETTER O
0x70      = U+0070 = LATIN SMALL LETTER P
0x2D      = U+002D = HYPHEN MINUS
0xC7 0x9D = U+01DD = LATIN SMALL LETTER TURNED E
0x70      = U+0070 = LATIN SMALL LETTER P
0xC4 0xB1 = U+0131 = LATIN SMALL LETTER DOTLESS I
0x73      = U+0073 = LATIN SMALL LETTER S
0x64      = U+0064 = LATIN SMALL LETTER D
0x6E      = U+006E = LATIN SMALL LETTER N

They are just unicode characters.

Look at source of web page:

function flip() {
    var result = flipString(document.f.original.value);
    document.f.flipped.value = result;
}

function flipString(aString) {
    aString = aString.toLowerCase();
    var last = aString.length - 1;
    var result = "";
    for (var i = last; i >= 0; --i) {
        result += flipChar(aString.charAt(i))
    }
    return result;
}

function flipChar(c) {
    if (c == 'a') {
        return '\u0250'
    }
    else if (c == 'b') {
        return 'q'
    }
    else if (c == 'c') {
        return '\u0254' //Open o -- copied from pne