I am not sure whether this has been discussed anywhere; if so, please point me to the right place. Still it shouldn't hurt to discuss it anyway.

With the site growing there will be an increasing need for including images into answers (I find they help a huge deal in certain cases; one picture is worth a 103 words, etc.). But what about copyright issues? I guess most of the authors (if they can be find, that is) wouldn't mind but it would still be correct to ask them, right (and not just because they might sue you)? On the other hand, it seems strange not to post an answer while waiting for a response from the author.

So, is there any policy about these things? Or is it perhaps no big deal, with issues being solved a posteriori after author finds his copyright is being infringed?

  • $\begingroup$ I think my answer on meta.math.SE applies here too. meta.math.stackexchange.com/questions/529/… $\endgroup$
    – kennytm
    Jan 12, 2011 at 16:07
  • $\begingroup$ @Kenny thanks but I am not sure it answers my question. Should I or should I not contact the author before (or at least after?) I use their image? $\endgroup$
    – Marek
    Jan 12, 2011 at 16:28
  • $\begingroup$ I used to think that when you linked an image "from a web site", that link would be maintained - and so it would automatically show the source of the image. But I just looked at a recent answer of mine and realized that a copy is made, and the link ends up being to imgur, not the source. This means I have some editing to do (if I can still find the sources...). Leaving this comment here in case others were under the same misapprehension. $\endgroup$
    – Floris
    Aug 5, 2014 at 7:46

3 Answers 3


The policy on this has changed since my answer was originally posted, so I thought an update would be in order. If you include content from another site, there are two separate reasons that it might be problematic: copyright violation, and plagiarism.

  • Plagiarism is the inclusion of any content taken from another source, unless the content is quoted and the source is acknowledged. Our rule on this site is that plagiarism is not acceptable, and plagiarized content will be removed or the post will be edited to quote and cite it, as we discover it.
  • Copyright violation is the copying of content from another source in a way that doesn't satisfy certain legal conditions. It is illegal and you shouldn't do it, but since Stack Exchange now has a formal process to handle DMCA takedown requests, moderators do not deal with copyright violations. If the content is also plagiarized (which is often the case), we'll delete or edit it for that reason, but we don't take any action because of a copyright violation. The SE team will delete content used in violation of copyright when they are made aware of it through a DMCA request.

To include content from other sources in your posts, you need to avoid both kinds of problems. Avoiding plagiarism is generally straightforward; always cite and quote your content. Avoiding copyright violation is a little more complex; yes, you should check that the material is available under a compatible CC license at the original source, or that the part you are using constitutes fair use, or try to get permission from the copyright holder, but in practice there may not be any consequences for not doing so if the copyright holder doesn't notice.

  • $\begingroup$ Thanks David. So should I go over my answers and sort this out? Because it so happens that I often used generic images found on Google Images and most of them probably won't be CC. $\endgroup$
    – Marek
    Jan 12, 2011 at 19:37
  • $\begingroup$ @Marek: yes, I think that would be a good idea if you have time for it. $\endgroup$
    – David Z
    Jan 12, 2011 at 19:40

As long as Stack Exchange provides a mechanism for complaints about copyright and is willing to take down copyright material as appropriately requested, I would have thought that widespread "fair-use" provisions would cover the use of even copyright material, particularly if the source is clearly acknowledged.

I would expect fair-use to apply if the item used is a small part of a larger work, but it is not prima facie obvious that reusing a single image would be "fair use" (that image might be one of a set of illustrations intended to be licensed for use individually). I would hope that a combination of common sense, reasonable efforts and fair-use would benefit all concerned. There is no guarantee that any re-use is necessarily valid (how do you know that the person you emailed for permission to reuse is in fact the copyright holder?), so why not strike a reasonable balance?

  • $\begingroup$ Thumbs up for "fair use" $\endgroup$
    – Deepak Vaid
    Jan 31, 2011 at 21:18

This answer about nanotubes included a very interesting (at least to me) diagram. I thought the author really took the time to conjure up some TikZ magic. Eventually, I found this paper:

The electronic properties of graphene
A Castro Neto, F Guinea, N Peres, K Novoselov, A Geim (2009)
Reviews of Modern Physics 81 (1) p. 109-162

and the exact same image was in Figure 2.

Shall we have a policy regarding citing sources?

I, for one, am preparing for graduate school, and I would like to learn how to find my way around the field I am applying to; so knowing which important papers to read would be very helpful for community members like me.

I almost added a comment to the answer regarding citing the source, but I didn't know how to play the role of "plagiarism police".

  • 1
    $\begingroup$ I agree that as a matter of habit any sources from which material - images, text, etc. - is used should be cited. You can always leave gentle reminders without leaving any impressions of "plagiarism police brutality". $\endgroup$
    – Deepak Vaid
    Jan 31, 2011 at 21:17
  • $\begingroup$ to be fair though, sometimes finding the sources for diagrams can be annoying. I have a huge backlog of interesting diagrams that reverse engineering the source for would be nightmarish. I'd say we should encourage people to cite, but not demand it. $\endgroup$
    – Skyler
    Aug 8, 2014 at 6:49

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