Is a URL starting with // valid?

user_622081 0
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We can see many HTML page using src="//example.com/myjavascript.js" to include a .js and let the browser use http:// / https:// depending on the current scheme of the page URL.

Is this a valid URI ?

url
3 Answers

It is valid indeed and I have just learned this in the hard way!! We broke a customization feature so you should always validate an URL like this (in .NET): Pay attention to:

  • White spaces (Trim)

  • "scheme relative" URI (UriKind.RelativeOrAbsolute)

    public bool IsValidUrl(string resourceUrl)
{
    Uri uri;
    if (Uri.TryCreate(resourceUrl.Trim(), UriKind.RelativeOrAbsolute, out uri))
    {
        return uri.IsWellFormedOriginalString();
    }

    return false;
}
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