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Working example on https://去.cc


This project is a proof-of-concept to make a better and more interesting URL shortening service. It leverages Unicode character blocks to offer novel numeric characters (in Chinese, Korean, anglosaxon runes, braille, and even emojis).

Most URL shortening services use only a base-62 alphanumeric key to map to a long-url. Typically, the base-62 characters include 26-uppercase letters (ABCD...), 26 lowercase letters (abcd...), and 10 digits (0123...), for a total of 62 characters. Occasionally they will include an underscore or dash, bringing you to base-64. This is all perfectly reasonable when using ASCII and trying to avoid non-printable characters. However, nowadays with modern browsers supporting UTF-8, and offering basic rendering of popular Unicode character sets (中文, 한글, etc), we can leverage a global set of symbols!


Why not!

To be fair, there are numerous problems with URL shortening services, from scammers to security issues. However, most people use a URL shortening service as a kind of novelty. Why not make the short URLs more interesting to look at?

For me, this is a personal project. I don't plan to offer it in any serious production capacity, other than for my own amusement, and also as a proof-of-concept of what a URL shortening service could do.


In short, Punycode with Unicode numeric bases.


Punycode is how we can get a short domain name, like 去.cc

Punycode is a transcoding of Unicode characters into a subset of ASCII characters (specifically those ASCII characters used in domain names). Punycode is used for internationalized domain names. For example, the domain 去.cc in punycode is All punycode domain names begin with the prefix "xn--". Older browsers that don't support internationalized domain names will simply gracefully degrade to the punycode representation. Modern browsers will display the internationalized domain names perfectly fine.

For reference, 去 (pinyin: qù) is a Chinese character that means "to go", as in 去商店 (go to the store) or 去學校 (go to school).

Unicode and UTF-8

Unicode is the industry standard for character coding, covering over a hundred thousand characters across modern as well as ancient writing scripts (with over a million possible characters). UTF-8 is the encoding standard used by almost all webpages. UTF-8 is variable width (1 to 4 bytes per character), and is completely backwards compatible with ASCII. This means ASCII strings will perfectly match their corresponding UTF-8 strings. UTF-8 also supports multi-byte Unicode encodings.

Unfortunately, browser support on upper Unicode blocks varies wildly (and sometimes requires additional language packs installed on your operating system), although increasingly most browsers offer at least one font capable of rendering most of the common Unicode blocks. And this seems to improve every year.

Unicode as a Numeric Base

One of the larger contiguous Unicode ranges that seems to have decent support on modern browsers is the initial CJK block as well as Korean Hangul syllables. Why are these interesting? Well, rather than a base-62 or base-64, we can use CJK and Hangul syllables to create extremely large numeric bases.

Extremely Large Numeric Bases

The CJK range of 4e00 to 9fea seems to be adequately supported, as well as the Hangul syllable range of ac00 to d7a3, this would give us a base-20971 and a base-11172 respectively.

For example, in a base-62 scheme, you may have a typical short URL that looks like this:


However, the x404 Novelty URL Shortener would look something like:


Taken to extremes, what if we're building a database of lots and lots URLs, let's say 9,223,372,036,854,775,807 (nine quintillion two hundred twenty-three quadrillion three hundred seventy-two trillion thirty-six billion eight hundred fifty-four million seven hundred seventy-five thousand eight hundred seven). This is the largest signed-64-bit integer on most systems. Even with that many URLs, we'd end up with short URLs that look something like this:


The CJK and Hangul examples are 6-characters shorter than their base-62 counterpart. In practice, I'm not sure anyone will ever need to map nine quintillion URLs. There aren't that many URLs, although there are billions of URLs. Let's say we're dealing with 88-billion URLs. In that case it would look like this:


NOTE: while the character-length of the Chinese string is less than the base-62 string, each of the Chinese characters represents 3-bytes in UTF-8. This will not save you bandwidth, although technically neither does ASCII, but it's worth mentioning nonetheless.

Other Novelty Bases

Unicode is full of fun and interesting character sets, here are some examples that I have built into x404:

# base-10   922111
base62:     LSR3
top16:      eewwt
CJK:        鶱丫
hangul:     쏉걒
dingbats:   ➚✴✙
braille:    ⣚⡴⡙
alchemical: 🜩🝓🝅
anglosaxon: ᛡᛇᛞᚻᚢ
greek:      οΒΦδ
yijing:     ䷫䷔䷫䷃
  • top16: The top-16 most common letters in English (where f maps to 0). This is a subset of base-62, and I find it often produces sequences that are easier to remember, albeit longer than base-62. To avoid collisions with base-62, x404 will prefix a "-" in front of any base-62 strings that are composed of top16 characters, e.g., "-ate".
  • CJK: The base-20971 Chinese characters. This potentially can grow to well over 80,000 -- depending on future browser support of the CJK block extensions. Also, these are really beautiful.
  • hangul: The base-11172 Hangul syllables. Note: Hangul is a phonetic alphabet with only 28 characters, however, for readability, Unicode includes 11,171 combinations of those 28 Hangul characters. This makes it useful as an extremely large numeric base.
  • dingbats: Precursor to emojis, dingbats provide a base-192.
  • braille: 8-dot Braille patterns provide a base-192.
  • alchemical: alchemical symbols provide a base-116.
  • anglosaxon: Anglo-Saxon Runes provide a mere base-29.
  • greek: Greek provides a base-49.
  • yijing: The I Ching (易經, yijing) hexagrams provide a base-64.


For use on 去.cc and



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