You may have noticed that I've avoided using the word 'Cockney' in the answer above. This is because the accents you are referring to probably aren't Cockney at all. The traditional speech heard in the markets of London's East End has all but disappeared. Nowadays, the Cockney accent is only used by a relatively small proportion of older Londoners, and it is likely to vanish entirely in a few decades. Estuary English took over several decades ago, and most of today's young generation of Londoners speak in what is known as Multicultural London English . This is a set of speech patterns which is heavily influenced by Caribbean and south Asian speech, and is very different indeed from the traditional London accents of a generation or so ago.

London speech is not dissimilar to the accent used by by millions of native speakers throughout the whole of the south of England. It's also an accent that we hear all the time on TV, radio and films. People from, say, Manchester or Glasgow speak very differently from Londoners, but we are all so used to hearing southern English voices in the media that this accent presents very little problem for any of us. ( The same goes for American accents, by the way - constant media exposure means that we all understand American English without any trouble, but that's another story). As Kate says, it might take a moment or two to attune our ears to the speech of another region of the British Isles : for example, if we switch on to a TV drama set in Liverpool or Dublin, we'd have to listen harder for a few moments. We might even miss a word or two if the speech is rapid or the language is colloquial, but we would still understand what was being said. And if there is an odd word which we don't catch, we can always infer the meaning from the context. English is not like Arabic, which has a totally different and sometimes mutually incomprehensible dialects in different regions. Nor is the UK like Italy or the German-speaking countries, which have dialects with different grammar and vocabulary. The English spoken by most people in the UK is actually the 99% the same wherever you are - it is only the accent which varies. We have all heard these accents before, so it's simply a case of tuning in the right accent.

Hi, Yorkshire native here. I understand the Cockney accent with no trouble but the dialect is very difficult since they use a completely different set of words. I can sometimes figure it out from context but it takes a minute to think.

I speak "received" English. My brother in law is a Cockney and I find the accent easy enough to understand, but then the accent is well known, on British TV etc. Some of the words and phrases though are often beyond me. There are not many Cockneys and the dialect/ accent is changing. https://en.wikipedia.org/wiki/Cockney

It's easy. I don't agree that Cockney speakers use a completely different set of words but there are, of course, some local words. I note from your profile you rate your English level as 2 bars. At this stage I wouldn't worry about trying to understand Cockney unless you live in London.