CSS selector case insensitive for attributes

It now exists in CSS4, see this answer.

Otherwise, for jQuery, you can use...

$(':input[name]').filter(function() {
   return this.value.toLowerCase() == 'search';
});

jsFiddle.

You could also make a custom selector...

$.expr[':'].valueCaseInsensitive = function(node, stackIndex, properties){
     return node.value.toLowerCase() == properties[3];
};

var searchInputs = $(':input:valueCaseInsensitive("Search")');

jsFiddle.

The custom selector is a bit of overkill if doing this once, but if you need to use it many times in your application, it may be a good idea.

Update

Is it possible to have that kind of custom selector for any attribute?

Sure, check out the following example. It's a little convoluted (syntax such as :input[value:toLowerCase="search"] may have been more intuitive), but it works :)

$.expr[':'].attrCaseInsensitive = function(node, stackIndex, properties){
    var args = properties[3].split(',').map(function(arg) {
        return arg.replace(/^\s*["']|["']\s*$/g, '');  
    });
    return $(node).attr(args[0]).toLowerCase() == args[1];
};

var searchInputs = $('input:attrCaseInsensitive(value, "search")');

jsFiddle.

You could probably use eval() to make that string an array, but I find doing it this way more comfortable (and you won't accidentally execute any code you place in your selector).

Instead, I am splitting the string on , delimiter, and then stripping whitespace, ' and " either side of each array member. Note that a , inside a quote won't be treated literally. There is no reason one should be required literally, but you could always code against this possibility. I'll leave that up to you. :)

I don't think map() has the best browser support, so you can explictly iterate over the args array or augment the Array object.

CSS4 (CSS Selector Level 4) adds support for it:

input[value='search' i]

It's the "i" at the end which does the trick.

Broader adoption started mid-2016: Chrome (since v49), Firefox (from v47?), Opera and some others have it. IE not and Edge since it uses Blink. See “Can I use”...