# Links / URLs containing special characters are not recognized by markdown

In this answer, I linked to some page within the Wolfram alpha site, and the links did not appear. For example, I will try to link the last word in this sentence. Here is the URL I was trying to link to

http://www.wolframalpha.com/input/?i=Plot[%281%2Be^%28-%282%29v%29%29^%28-2%29+%2B+%282%29+%281%2Be^v%29^%28-2%29%2C+{t%2C-0.5%2C+0.5}]

I suspect the problem is that Wolfram alpha uses square brackets in its URLs. If this could be fixed, it would be nice.

• I am calling this status-bydesign because it is not really a bug, just how these special characters are treated. If you want to request better parsing for URLs, repost on meta.stackoverflow as a feature-request, but I guess that the stackexchange team will decline/defer it since a reasonable workaround exists. Aug 9, 2010 at 16:02
• @Kaestur: At least for this user, it should be solvable by meta.stackexchange.com/questions/60211/…. I hope it won't be [status-declined] :) Aug 9, 2010 at 18:49
• "it is not really a bug, just how these special characters are treated" — I don't get it. These special characters are being treated not the way we want, so it is a bug. ("That's how it's implemented" is not the same as "That's how it's designed".) Aug 10, 2010 at 5:31
• @ShreevatsaR: those special characters are not technically allowed to be in URLs (not just an issue of what the site will accept). I think the best solution is probably the one suggested on meta.SO (KennyTM's link, above). Aug 10, 2010 at 5:34
• How can this be by design? Is forcing users to use silly tools like URL encoders to write links to Wikipedia (of all places!) part of the design?! If the design does not contemplate making it easier for users to provide information, well, I am sure someone can come up with a better design! Nov 24, 2010 at 17:17
• @Isaac: those characters are not allowed in a technical sense, but humans do write them. Since this software is intended to be user by humans... Nov 24, 2010 at 17:19

Since this was asked, we have improved ctrl+l aka the link toolbar button to encode any oddball characters in links inserted into posts:

The Wolfram Alpha link from above

Note that it is properly encoded, etc.

Some browsers also now automatically "fix" these oddball characters when copying from the address bar by encoding them on your behalf. A few tests with http://en.wikipedia.org/wiki/Dunning–Kruger_effect produced...

• Chrome 14: http://en.wikipedia.org/wiki/Dunning%E2%80%93Kruger_effect
• Firefox 6: http://en.wikipedia.org/wiki/Dunning%E2%80%93Kruger_effect
• IE 9: http://en.wikipedia.org/wiki/Dunning–Kruger_effect
• Opera 11.5: http://en.wikipedia.org/wiki/Dunning–Kruger_effect
• Safari 5.05: http://en.wikipedia.org/wiki/Dunning–Kruger_effect

So Chrome and Firefox have the most desirable behavior here, IMO.

• For Firefox 6.0.2 this is almost true. If you make any edits in the address bar before you copy and paste (even if you restore the edit), then the pasted version will no longer be encoded. I experienced this with my fat fingers trying to hit CTRL+C and missing. Sep 27, 2011 at 0:40

Two more workarounds:
Use a tool like this to encode the URLs
Use a URL shortening service like this

The second one is less good, because it relies on an outside party to guarantee that your answer/comment continues to make sense.

Many special characters need to be escaped, e.g. Plot[x^2,{x,-1,1}], the link http://www.wolframalpha.com/input/?i=Plot[x^2%2C{x%2C-1%2C1}] won't be recognized, because ^, { and } are special characters and need to be escaped, like http://www.wolframalpha.com/input/?i=Plot%5Bx%5E2%252C%7Bx%252C-1%252C1%7D%5D.