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The ID space for Imgur's IDs is 5 characters of alphanumeric characters. I noticed that i.sstatic.net has opted instead for 8 characters, while still supporting the 5 characters for images from the Imgur era.

I'm curious what the rationale is for the expansion.

I don't hold anything against the decision. But I am curious. I'd have thought it would have been simpler to keep things consistent. And the Imgur era images only consumed ~2.5% of the 5-character ID space (How much of Stack's imgur image-ID space has been consumed?), so to be honest I'd be surprised if dealing with collisions was a major concern.

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    Might also be to make it harder to "guess" and reach images at random, though there isn't "private image" feature, so it's just a wild guess. :) Commented Apr 30 at 21:05
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    The main public Imgur service uses more characters now. Commented May 1 at 1:06

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Even if the chance was small, we still would have had to deal with collisions when our unique ID generator was put into place. It was easy enough to pick a new length to avoid any potential collisions. Six characters also had the potential of collisions because some five-character images also included a sixth character used to denote thumbnails/resizing.

It also gives us the added benefit, if ever needed, of knowing if an image originally came from Imgur or our new service.

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  • I still find it hard to imagine those problems (collisions and differentiating eras) being more difficult to solve without expanding the ID space.
    – starball
    Commented May 1 at 0:32
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    @starball well, even with minimal gain, it's zero effort, zero downsides - so can't see why not. :-) Commented May 1 at 11:50
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    @Troy maybe worth to mention your ID generator use only lower case letters, while imgur's also use upper case? Or did I get it wrong when doing some trial and error today to check the algorithm? Commented May 2 at 13:45
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    I can see no upsides to documenting (even as lightly as "the id is comprised of lower case letters") the current generator algo... It'd make the id format pseudo-contractual when there's nothing to gain by doing so
    – Rob
    Commented May 2 at 14:10
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    There is nothing secret about it. The ids are alphanumeric, upper and lower case. My own profile image has uppercase letters in it: i.sstatic.net/vTsnIREos.jpg
    – Troy Gould StaffMod
    Commented May 2 at 15:04

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