The Web is the ultimate database of the English language. All sorts of expressions are stored out there. If you want to use the phrase, say, "different than ". Does it exist? You are not sure.
The best option is to run Google and use it to consult the world's websites containing the expression.
And here it is. There is no doubt the expression is in wide use. Almost 5 million pages contain it.
But let's try "different from" now.
Well, there is no doubt that statistically, throughout the English world as it appears on the Internet, the expression different from is more than three times as frequent as different than.
So now you know. Every time you question an expression, wondering about its real construction, just 'google it' to make sure.
If an expression appears in small numbers (e.g., a hundred or so), it means that the sites using it are wrong. It happens for example, I'm sorry to say, with French or Italian sites, where webmasters often think they write English but rarely bother to check out.
Next time to directly get to Google instead of reaching this page, click on the right part of the button, on Google itself !