I have noticed that even though the displayed image here is limited to only 630 pixels wide for the display (via height and width settings in the HTML), there can still be a 10-megabyte image sitting there behind it — so that when you bring up the page, your browser is slowly grinding through, all just to fit in that little box. In fact, as far as I can tell, there seems to be no limit to the size of images that Stack Exchange sites will autoload into people’s browsers. It does not matter whether it is 100k or 100 megabytes, or even larger. Anything goes, no matter what. This quite surprised me.

My question is this: is this no-size-limits-on-images thing here by design and intent? If not, then if it is just an accident of the implementation, is it a desirable feature or an undesirable one?

Perhaps I am wrong, but it seems odd to me that people can embed gigabyte (or whatever) images in their postings without any warning to other users, nor provision to limit their exposure. Some people really do pay for bandwidth, or only have so much of it. That’s why most sites, even Wikipedia, carefully set size limits on images that are diplayed on the main page without people clicking through. It seems a shame that rate-capped users would have to disable all images for fear of hitting a giant image on an SE site.

Is there any sort of notion that there might be a size above which it becomes a burden on other users, and is therefore discouraged? If so, what is the appropriate action if you stumble on a post with one of these gigantic images?

This arose in chat, where there is no opportunity to have a thumbnail that click-throughs to the full-sized image. It is worse there than on the main site. That’s because on the main site, if you want, you can arrange for a thumbnail to be displayed which if clicked through, takes you to the full-sized image. For example, like this:

That uses the trick of imgur thumbnail magic with the “l” suffix mentioned in this answer, like this:

For example, like this:  <a href="https://i.sstatic.net/CLQzM.jpg"><img src="https://i.sstatic.net/CLQzMl.jpg"></a> 

I was somewhat surprised that the upload mechanism did not already do that automatically. It seems to me it could be made to, so that only if you click on the image do you pay the full cost. Of course, this would only work for imgur uploads, not arbitrary image links.

And while conscientious users can do such a thing on the main site, that wouldn’t work in chat. It would require some coding changes, since you cannot use real HTML there as I have here.

Am I missing something obvious, or is this a less than optimal state of affairs?

Edit: I found several tangentially related postings, of which the question on “Please do something to encourage people to scale down their giant heavyweight photos” seems the most interesting and relevant.

  • You might want to add that users whose data are dear to them, like the tethering, are probably most in need of this. Otherwise they are forced to turn off image loading in their browser. Most browsers have no built-in option to do this on selected websites only. Commented Jan 13, 2013 at 6:13
  • Very related here meta.stackexchange.com/q/101439 and somewhat related, with some interesting discussion here: meta.stackexchange.com/q/9397 meta.stackexchange.com/q/15029 meta.stackexchange.com/q/75815
    – tchrist
    Commented Jan 13, 2013 at 6:17
  • You might also consider changing your title into something more specific and constructive, such as "can automatic loading of huge images in chat be solved?". Commented Jan 13, 2013 at 6:32
  • Can you give some concrete examples of where this is actually a problem? As it stands, this is pretty much a theoretical post.
    – balpha StaffMod
    Commented Jan 13, 2013 at 9:15
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    @balpha I remember an instance in the Teacher's Lounge on chat where someone posted several photos from their camera, causing quite a bit of lagging until the photos were deleted. Commented Jan 13, 2013 at 9:20
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    @balpha It is a problem on sites where users upload images from their digital camera, e.g. DIY. Many users don't bother to resize the images (see this example from the DIY frontpage where a mod then later reduced the image size). I don't care very much about this on my desktop, but it would be rather annoying to waste the bandwidth on my phone. Commented Jan 13, 2013 at 9:31
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    @balpha Automatic loading of images in chat also allows one to trace IP addresses, which seems like a security bug.
    – tchrist
    Commented Jan 13, 2013 at 15:01
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    – balpha StaffMod
    Commented Jan 13, 2013 at 15:05
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    @balpha Yes, I know: meta.stackexchange.com/questions/55665/… If Stack makes it a policy of protecting users’ IP addresses, this seems to go against that. It is worse in chat, somehow. You usually only get within a few miles of someone, not their exact street location, but it is still a bit unsettling.
    – tchrist
    Commented Jan 13, 2013 at 15:08
  • @balpha This should be tagged status-completed since we are limited to 2MB on site and in chat.
    – Rob
    Commented Mar 30, 2019 at 8:23
  • @Rob the limit is only for images uploaded to SE. One can still embed any image using raw HTML or markdown, so not sure it's really completed. Commented Apr 2, 2019 at 12:51
  • tchrist, is this question about the image uploader (now fixed), or about catching that what's behind an arbitrary img tag is huge and not letting it through? If the latter, can you edit to clarify and I'll remove the status tag? Commented Apr 2, 2019 at 15:20
  • @ShadowWizard The above question, exactly as written, is about being able to upload enormous images 6 years ago; the limit today is 2MB. An entirely different bug mentioned in balpha's comment (and your's) is the ability to have an image load in the user's browser that isn't from an upload to SE - that is an enormous security concern, but not the subject of the bug above. IF the OP expands the scope of their question it will be a partial duplicate.
    – Rob
    Commented Apr 2, 2019 at 16:53

2 Answers 2



It seems undesirable for a website such as this to have all users present in a chat room automatically download all full images behind posted image links. This should only happen after a thumbnail is clicked. How can this be achieved?

  • Whenever you post a link to an image in chat, like http://www.website.com/image.jpg, the image should be automatically uploaded to Imgur; then in chat a thumbnail taken from Imgur's automated thumbnail system should appear. Clicking on the thumbnail in chat should link to the full image.

(This automatically created thumbnail is basically the link to the Imgur file with l stuck before the extension—at least that is how I believe it works now on Imgur: if you have an image on Imgur at, say, http://i.imgur.com/my50D.jpg, there is always an automatically created thumbnail at http://i.imgur.com/my50Dl.jpg. Imgur has other thumbnails too, at different sizes, with m for medium and a few more.)

  • Al an alternative, this could be done within the browser of whoever posts the link, if possible. Whenever you post an image link in chat, the image is automatically (and invisibly) downloaded by your browser in the background, and your browser creates a thumbnail. Then the thumbnail is uploaded to Imgur, and it is posted in chat, linking to the full image on http://www.website.com/image.jpg. All this happens automatically, and only once, at the moment you post a link to an image in chat. The browsers of everyone else in the room then only see the thumbnail, which links to the original image http://www.website.com/image.jpg if you click it.

This way, Imgur is not unnecessarily burdened with storing and processing large images: only the uploader's browser needs to do some extra work, and that only once. On the other hand, duplicating the images to Imgur prevents link rot. I'm not sure how difficult this would be to implement; can it be done with Javascript?

This should only be necessary for images over a certain size (be it in KB or in pixels); would that be hard to implement? It is more convenient if images under, say, 100 KB are posted directly as now.

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    Wait, your second alternative is to prevent downloading a huge image by... downloading it in the background?
    – balpha StaffMod
    Commented Jan 13, 2013 at 8:17
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    @balpha: The poster's browser downloads it in the background, from whichever website his link refers to. His browser creates the thumbnail and uploads it. The browsers of everyone else present only download the thumbnail afterwards. Our main concern is that currently everyone present in the room downloads the entire image as soon as any link to an image from a website is posted in-line / one-boxed. Commented Jan 13, 2013 at 8:54

One complication is SVG images. An SVG map from Wikipedia was posted in Linguistics chat, http://upload.wikimedia.org/wikipedia/commons/7/76/Berne_Convention_signatories.svg.

Wikipedia maps are fairly detailed and can be several megabytes. This image was enough to make Firefox visibly slow down.

I suspect someone could perpetrate a denial-of-service on everyone in a chat room simply by posting a huge SVG image, large enough to make people's browsers unusable and possibly crash.

In order to prevent this, we would have to detect SVG images and render them to PNG. (Having Imgur support this would help.)

(In fact, you can do the same thing on the main site, using ![blah](http://upload.wikimedia.org/wikipedia/commons/7/76/Berne_Convention_signatories.svg).)

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