Course Link Validator flagging working links

[kinoshr]

I've been using the Course Link Validator for the first time this semester.  After checking and fixing a number of links, many are still being flagged.  I even checked all of the links in Student View, and they all checked out.  Does anyone know how I can prevent the "good" links from being flagged?

[KristinL]

Hi Rory -

Which error does the link validator report? 

My guess is that there is a link that was inserted by a copy/paste to a URL within another Canvas course. You have permission to view that content, as does your student view. However, it would not work for other individuals who are enrolled. Could you double-check that your "internal" links stay within the course? Some times those can be tricky to find with a course copy.

[kinoshr]

Hi Kristin,

The error is "External links in this resource were unreachable:"

I wondered if that was the case, so I tried to completely delete the URL and re-enter it, but the same error pops up.  I found the URL from searching Google and copied/pasted that one, to make sure that it wasn't a permission thing.  

Or maybe I didn't do that correctly?  I can try to delete the entire page and rewrite it from scratch.  Do you think that might help?

Rory

[rmurchshafer]

Rory,

Two other things to consider

1. Does the page you are linking to take several seconds to load sometimes?  If so it could just be timing out when the link validator is running
2. Does the page you are linking to require some sort of login?  It could be the page works for you, but for other people in the class such as your students and the process running the link validator it does not work because they are not logged in.  I see this happen if the link is going to another Canvas course by mistake.
3. Are you sure it's the link you are testing?  Canvas sometimes creates what I like to call "ghost links".  This is a link on the page that is there, but not really visible to anyone.  I think it happens when someone has a link and then deletes the text without unlinking it first.  The result is often a link that you can only see in the html so it's not a problem for anyone, but the link validator catches is and throws up an error.  Only way I know to fix these are to dig in to the html code to look.

Those are just a couple of things to consider.  I've seen this happen a few times too and if the page works when I try it and I know it's not a log in issue, I usually just don't worry about it.

Rick

[kinoshr]

Hi Rick,

To answer your questions:

1.  The page doesn't seem to take very long to load

2.  Yes, students need to login to their school Canvas account in order to access any of the material.  That's the only login necessary.  I logged in using my student account and was able to see all of the links fine.  I checked where the links took me and they all took me to either the same Canvas course that I am teaching or a different site such as our school website.

3.  When the Course Link Validator pops up the link that is broken, when I click on it, it works fine.  It could be something like the ghost link thing or something else that is invisible to the naked eye.  

It sounds like I might have done all I can really do without possibly trashing affected pages and start fresh.  I may do this when I have more time, but if the students don't have any problem with broken links then I guess I'll try not to worry about it for now.  Thank you for your help!!

Rory

[MarkN]

I was having this issue happen too. Link Validator would say, "external links in this preview were unreachable."

The problem was #3 in what Rick describes: "ghost links" that were at the end of the content description, probably from having a link and then deleting it without first using the "remove link" function.

These ghost links are viewable and deletable from the html editor option, when editing a page. 

[sphinney]

I have been seeing this happen more and more over the years of using Canvas Link Validator, that it shows external links to be unreachable when they are not. I just ran link validation in one course and numerous sites that link validator said were unreachable, were not. There were no "ghost" instances of the links in the course (which shouldn't pose a problem to link validator anyway, as long as the site is reachable).

I'm going to go way out on a limb here and suggest a possible reason this could be happening. Please note that I am not at all an authority on how these things work, but just wondering if this might be a reason for some of these issues. I wonder if some websites are blocking PING or some other method by which link validator checks to see if a site is reachable. I say this because when I used PING to try and reach one of the sites that was definitely working, my PING results came back showing the site was not reachable.

Perhaps Websites are using some kind of blocking tool(s) to prevent DNS attacks, and the Canvas Link Validator is seen as suspect by those tools. Just wondering...?

[mzimmerman]

@sphinney 

That sounds possible, though I don't actually know how the link validator checks external links.  

My guess is that, rather than doing a ping, it looks for the response to an http query to the specific link.  A ping would not give any kind of indication whether a specific URL was reachable, and lots of web servers block ping connections.  So, I think there's something else going on, but without knowing exactly what link is throwing the error, it's hard to guess what...

[sphinney]

@mzimmerman Thanks for sharing your thoughts. As I said, I have no authority on this subject, and was just throwing out one idea. I may be totally off base, but I find it odd that it would report so many unreachable external links, unless there wasn't some underlying issue particular to those sites. 

In my latest Link Validation, it reports four unreachable Webpages, but all are very reachable when I simply click the link that Link Validator provides, they are not slow, and even going to the page with the offending link and searching the HTML, I find no odd "ghost" links.

Here's another think I'm seeing lately with link validator. When I uncheck "Show links to unpublished content" it updates the number of links that it is reporting, however in the list it still shows me those unpublished resources. So it really makes that feature useless, since I can't distinguish which of the resources it is listing are published ones and which are not.

[mzimmerman]

Hi @sphinney 

The first test when you're trying to assess the Link Validator results is, do the links work if you are in "Student View"?   It's not a perfect test for external links, but it's a start.

Honestly, I don't see the Link Validator tool's primary usefulness being for external websites, but for internal links within Canvas--tracking down embedded images that are not accessible to students, links to content that is not published yet, content with links pointing to a previous course, etc.

[sphinney]

Thanks for that @mzimmerman . I don't see how that applies to external links, though. External links will be "reachable" or not regardless of my role in Canvas. For example, a link to www.google.com if it returns as unreachable will be unreachable to teacher roles or student roles alike, since Google doesn't know my role in Canvas.

In any event, I did try it from the student role with the same results.

[mzimmerman]

Hi @sphinney 

The external link might be pointing to a resource that requires authentication, or a tool that takes pass-through authentication from Canvas?  Or it could be something that's blocked from some locations?  Just a guess--hard to know without knowing what the specific links are.

[sphinney]

Oh, I see you're thinking there, @mzimmerman . In this case, none of the external sites required login or had any kind of pass through from Canvas. They were just ordinary Websites that were reachable by anyone.

[diana_myershyat]

I have found this issue happens on certain websites, including NPR and LinkedIn. Also had an issue with University of Miami. I have no idea what the technical issue is, but I've learned to just ignore the error.