Vegans don't eat or drink any products that come from animals.
Some beer has Isinglass in it. IIsinglass is the dried swim bladders of fish, which is used as a refiner in certain beers and wines. Filings of the material are often used to ‘clarify’ the beer towards the end of the production process, often to help speed up the clarification of the drink.
Some brewers also wash their barrels out with water that contains fish scales and that stays in the beer.
In addition some beers and wines have these elements in them:
Gelatine: Clarifier obtained from the skin, connective tissue, and bones of animals.
Casein/Potassium Caseinate: Protein found in cow’s milks and often used as a clarifier.
Insects: Made into dyes and used for colouring.
Glyceryl Monostearate: Animal derived substance used to control foam.
Pepsin: Also used to control foam, it is sometimes derived from pork.
Albumin:Most common type in brewing is serum albumin, which is taken from animal blood.
Lactose:Beers labelled as sweet, milk, or cream stouts may or may not contain lactose. Sometimes the description refers to the texture and not the ingredient.
Egg White/Honey - used in wine.
I avoid these products in alcohol. I have a website with over 38K wines and beers in that tells me what's vegan and what's not. But with these small craft brewery's, you never know.
I wrote to No 1 Mile End Brewing company and they very kindly replied that all their products are totally vegan.
Since being vegan I check a lot of labels and do quite a bit of research and I was amazed at what crap was in beer (not just animal produce either, chemicals etc)
Here's a link to the basis of the above https://www.veganfoodandliving.com/feat ... l-alcohol/
I still like a pint or two and glass of wine though