Was is the difference between .jpg and .jpg-large ? It seems like I can just rename the extension and it'll still behave the same. But it also means that many programs that expect a .jpg or .jpeg extension will choke up on displaying .jpg-large (for example, when opening a file from within a program, when the file filter is by default stuck to *.jpg, or "All Images (*.png, *.jpg, *.bmp, etc...)"

It just seems like a dumb thing that serves no purpose that wasn't thought through and does more harm than good and probably popularized by some image upload web 2.0 service just to look cool.

I mean, I could understand if .jpg-large were actually so large that many normal programs have difficulty with them... but how is 1024x768 "large" by any means of the word, when we've had monitors at that resolution since 1999 at least (I think that was the exact resolution of the CRT monitor my family got about mid-1999). If the resolution of the images were greater than 4096x2048 or something, I could *kinda* see that there *maybe* might be a need for it.

It would make more sense if large files could be better compressed, and faster, at a higher quality with a newer algorithm, so .jpg supports another algorithm that most earlier programs aren't familiar with, so to preserve backward compatibility, .jpgs using the new algorithm use a different extension but still have the same image format... but I'm hypothesizing here, Wikipedia doesn't have any information, and my googling turned up too many irrelevant results.

So my question is, what is the purpose of this extension? If it has no purpose, who is responsible for this travesty?

[rollup="If you don't speak English, I Google-translated my question into 'Internet'."]
[/rollup]

Compare the jpg-large header with a standard jpg file. My guess someone meant to rename a regular jpeg, but misplaced the "-large", cause I don't know what you're talking about :| Where are these mysterious jpg-large files?

Some research has turned this up from a Chromium bug tracker issue.

Yeah. The extension is derived from the URL. The filename is determined to be "BBoix8aCAAAl9mK.jpg:large", and then sanitized to "BBoix8aCAAAl9mK.jpg-large". During sanitization we replace certain characters in the filename with '-'.

So I'm guessing that's the reason, it's not the website that's adding the extension, it's some kind of URL attribute which gets sanitized to jpg-large by the browser. All in all, looks like the website (here, Twitter, apparently) is misusing the HTTP protocol to store metadata which the browser then fails to interpret sensibly.

Oh good, that's exactly what is happening. So it is an URL parsing error, not some lame decision made by someone (well, it might be a bad decision on Twitter's part, but I don't know enough about web development to know if they are actually doing something dumb or not).

I use Google Chrome on Win7, and yes, they were twitter images. This has been occurring for at least a year or so, and I bump into it about once a month so I was mis-assuming it was an deliberate decision (especially since the misparsed extension "jpeg-large" looks human-chosen and intentional).

Thanks for figuring it out! I left a note on the Chromium bug-tracker to indicate the problem still occurs.

Here was the page that reminded me of this issue last night: http://news.yahoo.com/blogs/sideshow/fogmageddon--grips-seattle-194612028.html

3 of the 4 photos were from twitter users; I frequently download photos like that for game design or game area inspiration.