I just had an answer deleted by @Flexo that meets the criteria "barely more than a link to an external site". Those with sufficient privileges can see it here: different between CRC8 , CRC16 and CRC32?

All of the questions posed are answered completely, and much more, in the tutorial that I linked to. In my opinion, that is an excellent and complete answer, and it is very useful for others looking at those sorts of questions to be directed to that tutorial. In fact the questioner said exactly that: "Thanks for the link. It is very useful. I didnt find any good links like this."

So basically, I disagree with the criteria: "barely more than a link to an external site" being applied without thought or inspection. Such answers should be permitted when they are in fact answers and useful to others. There is no value in repeating the tutorial or parts of the tutorial in the answer.

Other opinions?

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    What happens when the tutorial you linked to goes away and the question is completely useless for future visitors? – Wooble Sep 18 '13 at 17:41
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  • That tutorial has been out there for 20 years, so I'm not real worried about it disappearing completely. I could improve the answer with the title of the tutorial, with which a google search shows the dozen or so places it is available. Except I can't improve the answer since it was deleted by a moderator. – Mark Adler Sep 18 '13 at 17:46
  • The answer to the question, which was very broad, requires most of the tutorial. So should I have simply copied the tutorial into the answer? It's about 90K. – Mark Adler Sep 18 '13 at 17:47
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    @MarkAdler: Which is why the question was just "put on hold as too broad" 2 minutes ago. – David Robinson Sep 18 '13 at 17:47
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    You should have just voted to close the question and posted the link in the comments as a reference. How can the question not be considered too broad when your answer is a link to a 37-page paper? – animuson Sep 18 '13 at 17:48
  • I can edit it, but I can't request undeletion. It says it was deleted by a moderator and can't be undeleted. – Mark Adler Sep 18 '13 at 17:54
  • @MarkAdler You can flag it, you can't undelete it yourself. That said, I don't see it as a complete answer even after your edit. The question, by your own admission, is too broad, and should just be closed. Post your link as a comment if you would like. – Servy Sep 18 '13 at 17:55
  • I have added the link as a comment. – Mark Adler Sep 18 '13 at 17:57
  • I see many questions on CRCs that are answered in this tutorial. If people would just read it. So if I put up a question something like: "Where can I find a really nifty tutorial on the theory and implementation of CRC algorithms?" and posted my own answer, would all that be deleted, held, disparaged as too broad and just a link? – Mark Adler Sep 18 '13 at 18:02
  • @MarkAdler: it would be closed either as Too Broad, or as Off Topic: "Questions asking us to recommend or find a tool, library or favorite off-site resource are off-topic for Stack Overflow as they tend to attract opinionated answers and spam. Instead, describe the problem and what has been done so far to solve it." – David Robinson Sep 18 '13 at 18:07
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    That tutorial has been out there for 20 years, so I'm not real worried about it disappearing completely. So every time someone posts a link-only answer, moderators should check out the link, figure out how long it's been out on the internet, and judge whether it is likely to remain working? There are many dead links in SO's old answers, so this is a very real problem. – David Robinson Sep 18 '13 at 18:11
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    You are misinterpreting what people are saying. It is not alright to just direct people to something offsite. An answer should stand on its own. By all means - add a comment with the link. I know I do that often enough. – Oded Sep 18 '13 at 18:34
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    @MarkAdler, the feature intended for that kind of thing is tag wikis, although they could use a bit of love and visibility. – jscs Sep 18 '13 at 18:52
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    By the way, it's great to see all the love you get here when you try to have a simple discussion about something. There must be great satisfaction in piling on with everyone else the negative ones on the question. I thought, apparently incorrectly, that this manner of topic was exactly what this meta forum was for. – Mark Adler Sep 18 '13 at 20:45


Because they are not answering the question. They are pointing to something that may contain the answer, may contain it but is buried somewhere, may simply be spam. There is no way to know until someone clicks and parses it.

If someone has an answer they should give it there and then and a link to something that supports the answer is just a bonus.

Additionally - links rot. If a link works today and is relevant, great. But what about tomorrow, when that server/site dies or moves links around without redirecting?

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    I would just like to add: Regardless of how good the link is, if people were allowed link-only answers, then people can simply google and potentially answer any question without actually knowing a single thing about the topic. That's definitely not good for the quality of the site. – gitsitgo Sep 18 '13 at 17:52
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    Another thing I am fond of adding regarding this: Stack Overflow is here to be a repository of questions and answers - not a collection of links. – Andrew Barber Sep 18 '13 at 19:31

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