Smelt vs smelled

As suggested by the Grammarist “smelled” is the more common form in AmE, while in BrE both forms are used:

In American and Canadian English, the verb smell makes smelled in the past tense and as a past participle.

Outside North America, English speakers use smelled and smelt interchangeably, and neither form is significantly more common than the other.

For North Americans, smelt usually means (1) to melt or fuse ores, and (2) any of several small, silvery fishes of the family Osmeridae found in fresh waters of the northern hemisphere. Smelt as a form of smell is not unheard of in North America, but it is rare appearing mainly in the rhyming jocular expression whoever smelt it dealt it (and its variants).

Smell has both an irregular and regular form. You can use both and both are correct. Brits use smelled and smelt interchangeably, but speakers in North America rarely use smelt.

But which is the most used one? Let's look at Google Ngram Viewer tool which displays a graph showing how phrases have occurred in a corpus of books over the years.

Let's look at the current online media:

New project to find out what Europe smelt like from 16-20th century – [BBC]

Yaoumbaev told CNN he smelt something extremely unpleasant –[CNN]

Source: en.learniv.com