Someone shared a link with me, which goes nowhere. The user was on a mobile device, and the link was sent to my Gmail account. I've asked if I can share the original link (might be sensitive) and haven't hear back yet.

I've found some similarly structure links via Google. Here's an example:


(It's all one link, just wasn't sure how else to force a line wrap in markdown.)

What I want to know is, what is the "leo://plh/" part about? I have basic understanding of URL structure, schemes, and URL encoding... or in this case, double-encoding? Not sure how / gets turned into *3, though.

This seems like something Google would've answered for me, but 20 minutes later I'm stumped. All I find is more examples of links that are formed this way, not an explanation of why.

ETA: It's been suggested this is a custom URI scheme - makes sense. But whose is it? Who / what uses it? Google "leo://plh/" and you'll see that various sites have these links, and they point to content on more than one other site.


I agree it must be a custom URL protocol. There are some security concerns and it would depend on if the developer who wrote the application had in mind when it comes to code injection, defend against malicious attacks, etc. But from your standpoint you wouldn't have anything to worry about I couldn't imagine. As for why it went nowhere, is probably because as it says above you don't have the application necessary to execute the protocol. It doesn't look like the protocol is registered to any well known application software, but perhaps it is part of the mobile application mentioned above.

Here is the documentation on the URI Scheme https://msdn.microsoft.com/en-us/library/aa767914(v=vs.85).aspx

Here is the documentation for registering a protocol handler for a custom url protocol. http://blogs.msdn.com/b/noahc/archive/2006/10/19/register-a-custom-url-protocol-handler.aspx?Redirected=true

and from what it looks like the protocol is leo:// which is tied to the custom application and then the link is encoded to remove characters that would be parsed by the browser and is an escaping option...I don't think that they meant to send you the link like that, however the application that they had sent it from encodes it in that format can be directly opened from that same application on your device without any error from the browser. My best guess without any documentation to look at



This URL has the format of a custom URI scheme or a URI used by Mobile Deep Linking.

What is the embedded link URL?

The full URL is:


Using %3a = :, *3 = /, and %2e = ., then the embedded link decodes to:


"But whose is it? Who / what uses it?"

There is a mobile app called LEO ("Saving you money, at the places you love.)"

This would be an obvious candidate for creating the quoted URI when the app is used to share a link ("You can then share the offer with your friends via Facebook or Twitter. Remember, the more people that use LEO, the more offers and more savings in the future.")

  • Looked into this - the LEO app is not the source, as far as I can tell. – selllikesybok Jul 10 '15 at 13:45
  • @selllikesybok For what it's worth the decoded link is www.rackspace.com/knowledge_center/article/cms-comparison-drupal-joomla-and-wordpress – DavidPostill Jul 10 '15 at 13:49

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