Overtourism

Bruges was uncrowded in mid-Sept 2018. Street scene had moderate/light crowds, art museums lightly visited.

You can always favor Ghent to avoid the overcrowding in Bruges.

I was in Bruges 4 years ago (July) and it was crowded but not horribly so. There were plenty of places that it wasn't crowded so it was easy to find breathing space. None of the museums were crowded at all and even the Bruges Madonna in the cathedral only had a few people around. Also the canals farther from the main square and around the Beguinage area were relatively peaceful and crowd free. As long as there are places to get away from the crowds I don't have a problem.

Bruges was uncrowded in mid-Sept 2018.

That was my experience as well. In early October 2018, I went walking around the old town around breakfast time and saw only a few people - some obviously residents and a few tourists with roller bags. It was the kind of near-solitude that I love when I travel. Later in the day there were more people, but it remained an obvious mix of locals and visitors. Not all that many people in the restaurants, either.

Go off season to this wonderful place, Brugge.
I too have seen the changes from my spring trip this yr to my summer trip 5 yrs ago.

Cruise ships and their passengers can become a nightmare.

A very drastical number you can see in Norway's Flam. The village has 350 residents - if two cruise ships are in the port, it is nearly impossible to find a local.

Hallstatt in Austria is another example.

Living some 40km away I visit Bruges a few times a month mostly during the week and it becomes more and more difficult to find days you have the place so-called for yourself. The weather must be then really bad like you can have for instance in February. A few weeks back Bruges just the day after Ascension Day was a complete madhouse.

More about overtourism in Bruges see this recently started thread:
https://community.ricksteves.com/travel-forum/belgium/bruges-trying-to-put-a-lid-on-short-term-tourism

Sad, I haven't been there yet but it was on my list and I really hate crowds. Well going off season should be better right? I mean, would the crowd be significantly reduced then?

The day after Ascension Day many in Belgium have a free day and do daytrips to Bruges, so it becomes way more busy as usual and the beaten path area is really (over)crowded. It’s better known as the golden triangle, that is the Lake of Love, Main Square, Burg Square and the streets in between. If you prefer to visit Bruges during calmer periods best is to avoid the days during special events like Ascension Day. And leaving the beaten path you will see Bruges is surprisingly quiet as the whole place is during the morning and evening.

During shoulder season Bruges will be lesser busy but there are always tourists, busy but it don’t have to mean it will be crowded. It depends how you look to it, till so far it's not every day a madhouse there. Not so long ago in February and March there were very few tourists and even with good weather you had the idea having the place to yourself. But this is rapidly changing even with bad weather visitors keep coming. I still have pictures of the Main Square of Bruges in Janauri of 1997 and there were hardly any people to see there, hard to imagine nowadays.

There have been a few articles about Bruges written recently. I haven't been there and would love to see such a beautiful city and its churches. I would hope visiting in the late autumn or early spring avoids these masses. The terrible part is that these mobs just come for the day; I would stay for a few days.

Continental, between going off season and staying for a few days, I would think you'd be fine. Many years ago we spent a week in Riquewihr, in Alsace, which was a heavily touristed village (nothing like places like Venice and Bruges, though). Things were quiet in the early morning, then the tourist buses arrived. But we were gone most of the time during the day, and by the time we got back, the buses had all left and it was pretty quiet again.

I had not heard the term "overtourism" before, but I am about to listen to this episode from today's Forum on NPR:

https://www.kqed.org/forum/2010101871871/coping-with-overtourism