What's up with this error?

Oops! Your edit couldn't be submitted because:

Your post contains a link to the invalid host ''. Please correct it by specifying a non numeric domain or wrapping it in a code block.

This is not because I typed a link to the address []( (though that should be acceptable, too). This is because I typed the bare IP address and it was auto-converted to a link and then the auto-link was rejected.

If you don't want this bare URL converted to a link, why don't you just... not convert it to a link? It seems silly to reject my post and make me wrap it in a code block manually when the software could just ignore it at the rendering stage.


The auto-link has been fixed:

But it still rejects links of the type [](, which is inconvenient when trying to tell people how to configure their router, web server, etc.


2 Answers 2


This comment is caused by a tool called the . It's new, and still in development. You can see some development effort at https://stackoverflow.com/review/broken-links; but all the buttons cause a 'dev only not implemented yet' error.

Your error is caused by the link validator assuming that all links should point to non-redirected live websites on the global internet. Yours does not. As a subset of this assumption, the link validator (author) identified a common problem: IP address links are broken quite often. For these reasons, the link validator does not allow your link to be posted.

I disagree with these assumptions. It's obvious to anyone with computer experience that is an invalid host. However, if you're writing about a local server running at this address, it makes sense. At work, we have an Ethernet-based development board which has a hard-coded IP address of, and many of our internal wikis contain links to this IP address: Clicking on a link, assuming that the reader has this configuration, will do something useful. Similarly, Stack Overflow has ostensibly broken links to http://localhost/ (834 posts) and http://localhost:8080/ (393 posts). They're the two most common 'broken links' on the site. In the first 10 instances I looked at, they were intentionally links - Someone attempting to follow the steps in an answer or reproduce the problem described in a question would be expected to want to click on these links.

This is, I believe, an instance of the link validator being overzealous.

grumble grumble....

Oops! Your answer couldn't be submitted because:

  • Your post contains a link to the invalid domain 'localhost'.
    Please correct it by specifying a full domain or wrapping it in a code block.
  • Your post contains a link to the invalid domain 'localhost'.
    Please correct it by specifying a full domain or wrapping it in a code block.

Because is an internal IP address, and if someone were to click it, chances are they would get a 404.

To fix, wrap your URL in the inline code block key `, and the editor will accept it.

  • 8
    Why should I do something that could be done automatically in software?
    – endolith
    Jun 1, 2012 at 15:08
  • 4
    @endolith god forbid you have to type an extra two keys. And besides, it's an error on your part to try to post a link to an invalid host, and not something the computer should clean up for you. Jun 1, 2012 at 15:10
  • Well, at home I would get the web interface to my cable modem... Jun 1, 2012 at 15:14
  • 4
    Posting is not the same as posting []( or any other form of link, nor is it necessarily an error. And if the computer shouldn't need to clean it up, then why does it need to detect it? The detection is the hard part, not linking it is easy.
    – user154510
    Jun 1, 2012 at 15:24
  • 4
    @RichardJ.RossIII - It's not necessarily an error to try to post a link to an invalid host. What if Endolith was writing an answer about setting up dmckee's cable modem? (or, knowing Endolith, setting up some embedded development board...) It's reasonable to expect that he'd want to link to an internal IP, and that readers following the answer would want to click on it. A warning might be nice, but the site doesn't need to and can't assume that he wants to link to an external, always-valid link. Jun 1, 2012 at 15:45
  • 6
    @RichardJ.RossIII: God forbid software does what the user wants, instead of rudely forcing them to jump through hoops to do what it wants.
    – endolith
    Jun 1, 2012 at 18:43

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