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What is &amp used for

Is there any difference in behaviour of below URL.

I don't know why the & is inserted, does it make any difference ?

www.testurl.com/test?param1=test&current=true

versus

www.testurl.com/test?param1=test&current=true

1 Answer

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& is HTML for "Start of a character reference".

& is the character reference for "An ampersand".

&current; is not a standard character reference and so is an error (browsers may try to perform error recovery but you should not depend on this).

If you used a character reference for a real character (e.g. ™) then it (™) would appear in the URL instead of the string you wanted.

(Note that depending on the version of HTML you use, you may have to end a character reference with a ;, which is why &trade= will be treated as ™. HTML 4 allows it to be ommited if the next character is a non-word character (such as =) but some browsers (Hello Internet Explorer) have issues with this).

HTML doesn't recognize the & but it will recognize & because it is equal to & in HTML

Another common error occurs when including a URL which contains an ampersand ("&"):

This is invalid:

a href="foo.cgi?chapter=1&section=2&copy=3&lang=en"

Explanation:

This example generates an error for "unknown entity section" because the "&" is assumed to begin an entity reference. Browsers often recover safely from this kind of error, but real problems do occur in some cases. In this example, many browsers correctly convert &copy=3 to ©=3, which may cause the link to fail. Since ⟨ is the HTML entity for the left-pointing angle bracket, some browsers also convert &lang=en to 〈=en. And one old browser even finds the entity §, converting &section=2 to §ion=2.

So the goal here is to avoid problems when you are trying to validate your website. So you should be replacing your ampersands with & when writing a URL in your markup.

Note that replacing & with &amp; is only done when writing the URL in HTML, where "&" is a special character (along with "<" and ">"). When writing the same URL in a plain text

email message or in the location bar of your browser, you would use "&" and not "&amp;". With HTML, the browser translates "&amp;" to "&" so the Web server would only see "&" and not "&amp;" in the query string of the request.

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