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[edit - Nevermind, solved below in the comments.] Does anyone know how these work long-term? This one shortens a URL to 4 characters, so for a potentially major

[edit - Nevermind, solved below in the comments.] Does anyone know how these work long-term? This one shortens a URL to 4 characters, so for a potentially major URL shortener, there is a relatively low number of possible outputs. Once they hit their limit, do they start erasing the oldest ones? The most inactive ones? For shorteners that give consistent shortened URLs (i.e. everytime you shorten the same input URL, you get the same shortened output URL), how do they deal with hitting their maximum?

JeremyBanks 16y ago
Once the 4-character paths are saturated they'll probably simply move to 5-characters. With respect to goo.gl, the help page lists these features: Immutable - once created by you, no one else can change them Irrevocable - once created, they do not expire. I think that most large shorteners don't automatically expire links. It would be pretty miserable if they did.
- zacharycohn 16y ago
  Yeah, I just ran the math. (numbers + lowercase + upper case)^num of characters 10+26+26 = 62^4 = 14,776,336. That's a reasonably large number (and then my friend just suggested the adding a character if they start to run out). Thanks!
acangiano 16y ago
> Once they hit their limit, do they start erasing the oldest ones? The most inactive ones? Let's do the math. If we assume that a service only uses a-z, A-Z and 0-9 as characters for the shortened URL, we have a set of 62 characters. /x -> 62 /xx -> 62^2 = 3,844 /xxx -> 62^3 = 238,328 /xxxx -> 62^4 = 14,776,336 /xxxxx -> 62^5 = 916,132,832 /xxxxxx -> 62^6 = 56,800,235,584 In the worst case scenario, the URL shortener will have to use a 6 character identifier at some point, giving them a complessive coverage of almost 58 billion URLs. The 4 characters they are currently using will only be enough for a while. They'll switch to 5 soon enough.
- jodrellblank 16y ago
  > The 4 characters they are currently using will only be enough for a while. They'll switch to 5 soon enough. Hmm... are they sequentially used? Bets on how soon?
- zacharycohn 16y ago
  56,800,235,584 URLs ought to be enough for anyone... :)
- toolate 16y ago
  It seems like a bad idea to differentiate between upper and lowercase case to me. I imagine most people reading a URL aloud would not specify the case. Perhaps they have done some testing.
- brfox 16y ago
  I tired about 10 random ones and 3 were real links. So are they approx 30% full already of the 4 character urls? I guess you better not shorten a url to a page you don't want to be public, because then the address will be easy to guess.

JeremyBanks 16y ago

Once the 4-character paths are saturated they'll probably simply move to 5-characters. With respect to goo.gl, the help page lists these features: Immutable - once created by you, no one else can change them Irrevocable - once created, they do not expire. I think that most large shorteners don't automatically expire links. It would be pretty miserable if they did.

zacharycohn 16y ago
Yeah, I just ran the math. (numbers + lowercase + upper case)^num of characters 10+26+26 = 62^4 = 14,776,336. That's a reasonably large number (and then my friend just suggested the adding a character if they start to run out). Thanks!

acangiano 16y ago

> Once they hit their limit, do they start erasing the oldest ones? The most inactive ones? Let's do the math. If we assume that a service only uses a-z, A-Z and 0-9 as characters for the shortened URL, we have a set of 62 characters. /x -> 62 /xx -> 62^2 = 3,844 /xxx -> 62^3 = 238,328 /xxxx -> 62^4 = 14,776,336 /xxxxx -> 62^5 = 916,132,832 /xxxxxx -> 62^6 = 56,800,235,584 In the worst case scenario, the URL shortener will have to use a 6 character identifier at some point, giving them a complessive coverage of almost 58 billion URLs. The 4 characters they are currently using will only be enough for a while. They'll switch to 5 soon enough.

jodrellblank 16y ago
> The 4 characters they are currently using will only be enough for a while. They'll switch to 5 soon enough. Hmm... are they sequentially used? Bets on how soon?
zacharycohn 16y ago
56,800,235,584 URLs ought to be enough for anyone... :)
toolate 16y ago
It seems like a bad idea to differentiate between upper and lowercase case to me. I imagine most people reading a URL aloud would not specify the case. Perhaps they have done some testing.
brfox 16y ago
I tired about 10 random ones and 3 were real links. So are they approx 30% full already of the 4 character urls? I guess you better not shorten a url to a page you don't want to be public, because then the address will be easy to guess.