How to Do a Case-Insensitive String Comparison

How to do case insensitive string comparison?

The simplest way to do it (if you're not worried about special Unicode characters) is to call toUpperCase:

var areEqual = string1.toUpperCase() === string2.toUpperCase();

Case-insensitive string comparison in C++

Boost includes a handy algorithm for this:

#include <boost/algorithm/string.hpp>
// Or, for fewer header dependencies:
//#include <boost/algorithm/string/predicate.hpp>

std::string str1 = "hello, world!";
std::string str2 = "HELLO, WORLD!";

if (boost::iequals(str1, str2))
{
    // Strings are identical
}

How do I do a case-insensitive string comparison?

Assuming ASCII strings:

string1 = 'Hello'
string2 = 'hello'

if string1.lower() == string2.lower():
    print("The strings are the same (case insensitive)")
else:
    print("The strings are NOT the same (case insensitive)")

As of Python 3.3, casefold() is a better alternative:

string1 = 'Hello'
string2 = 'hello'

if string1.casefold() == string2.casefold():
    print("The strings are the same (case insensitive)")
else:
    print("The strings are NOT the same (case insensitive)")

If you want a more comprehensive solution that handles more complex unicode comparisons, see other answers.

How to do a case-insensitive string comparison?

If you can afford deviating a little from strict C standard, you can make use of strcasecmp().
It is a POSIX API.

Otherwise, you always have the option to convert the strings to a certain case (UPPER or lower) and then perform the normal comparison using strcmp().

Case insensitive string comparison

This is fairly simple; you just need to call strtolower() on both variables.

If you need to deal with Unicode or international character sets, you can use mb_strtolower().

Please note that other answers suggest using strcasecmp()—that function does not handle multibyte characters, so results for any UTF-8 string will be bogus.

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