Is it good practice to have hyperlinks in bibliographies? Lately I have been thinking about what is the right way to cite other papers (i.e., what to put in the bibliography entries, in the section which is typically called "References"). As many papers are available online nowadays, it seems to me that bibliographic references should include, whenever possible, a link to the paper being cited: this is supported by the PDF format, and is easy to do (at least for works typeset in LaTeX: e.g., with \href{} or \url{}). Yet, strangely, I have never seen a paper whose bibliography entries consistently featured URLs or hyperlinks to the works being cited. Is it good practice to include hyperlinks in bibliographies? If yes, why is essentially no one doing it?

One possible explanation is laziness on the part of the authors, but, strangely, there are still many papers whose bibliography entries include information about volumes, series, and page numbers, even though in my field (computer science) I have never seen anyone look up a paper using this information: people just search for papers with Google using the title and authors every time (in other words, they work around the non-existence of a hyperlink which should be there). Maybe the explanation is that existing bibliography management tools make it easier to manage page information than URLs? But is this just inertia, or is there a good reason?

A side question is assuming you want to have hyperlinks in your bibliography, which hyperlinks should you use? I have a preference to link to open-access versions of the cited papers (i.e., which aren't paywalled, so everyone can follow the link), but this sometimes conflicts with other desiderata, such as having a stable URL (e.g., not a PDF on some author's personal web site), having a link which indicates the DOI of the paper, etc. Which criteria should one preferably follow? 

Another side question in this case is how should the links be formatted? One possibility is to write out the URLs explicitly, but this ends up taking a lot of space, and may be illegible, especially for long URLs. The other option is to use \href{}, i.e., put a hyperlink on the paper title, but this is probably not very discoverable, and it means information is lost whenever someone prints the paper. Which one is preferable, or are there other formatting options?

Edit: For papers submitted to publishers, indeed, it probably suffices to follow the publisher style (although the question remains of why so little publishers seem to be doing it). My question was more about preprints and author-final versions, prepared by the authors to be published online (e.g., on arXiv) independently from any specific publisher.

Related questions (with URLs ;)):


Should I include a DOI/website URL for a publication in dissertation bibliography?
Publishing DOIs instead of traditional references?
What are the downsides of using DOIs in reference sections of publications?
Maybe I'm a bit late here, but I do think it is among the best practices there can be. I also can't understand why journals' names are abbreviated. IMO providing links is really important for many reasons:


It provides quick access to the cited material (either text or anything else).
If a link is available, checking that source is (normally literally) one click away.
If it isn't, it can be a challenge to get it. If the link is a DOI or other persistent link, it ensures access even if the final link changes. If the link is not persistent, it provides some transparency: the material was online at URL "x" at day "y", so if it's gone it's not your fault but you stated every information you had, and your reader now has some more info to work with when trying to reach that same source (looking for cached/archived versions, maybe looking for other people referencing the same URL who might quote some bigger part or even have an offline copy, who knows...).
A reason for deliberately using a not-DOI URL: "People click on URLs that they understand and view as authoritative", so depending on the domain or subdomain of your cited material's URL, it could be a (not so) subtle persuasive use of that information in one's favor (either a publisher's, a government's, an international body's or any other institution's domain).


And these are just the ones that immediately come to mind now. But I think all the reasons that justify all the efforts to create the idea of DOI as a persistent link and maintain a whole infrastructure around it apply here as reasons to use it.

Actually, the real question could be why not use them (DOIs first, but links in general), and there are as many reasons for not using it as there are for abbreviating journals' names these days.

As to formatting, reason 1 above suggests not using "doi:10.1234/abcd1234" as this is not clickable (unless you manually make each one clickable by formatting it as link etc.), but rather something (automatically) clickable like "https://doi.org/10.1234/abcd1234". 

And providing the last date you had successful access to it is useful as well, for what I mentioned in reason 3 above. (Some styles suggest stating the date of your first access. I can't quite see why would this be more important.)