It's a question we get asked most weekends on the Beer Mile, usually by someone eyeing up a taproom pint with a slightly suspicious look: "hang on, is beer even vegan?" It's a fair question, because beer looks like the most plant-based drink going — water, malted barley, hops, yeast — and yet there's a genuinely animal-derived ingredient with a long history in British brewing. The honest, short answer is that most beer you'll drink today is vegan, especially anything on keg or in a can, but it's worth understanding exactly why, so you know what to look out for.
The short answer
Yes, the vast majority of modern beer is vegan. The core ingredients — water, malted grain, hops and yeast — contain nothing derived from animals. The exception that causes all the confusion is isinglass, a fish-derived fining traditionally used to clarify cask ale, and it's specifically a cask tradition rather than something you'll find in most keg or canned beer. Once you understand what isinglass actually does, the rest of the "is beer vegan" question becomes easy to answer for yourself, can in hand.
What is isinglass, and why is it in beer at all?
Isinglass is a form of collagen traditionally extracted from the swim bladders of certain fish, most commonly sturgeon historically and more often tropical fish like the Vietnamese pangasius today. Brewers have used it for centuries as a "fining" — a clarifying agent added to a cask of beer after fermentation to speed up the process of dropping haze-causing yeast and protein particles to the bottom, leaving a bright, clear pint above. It's a genuinely clever bit of traditional food science: the collagen carries a slight positive charge that attracts the negatively charged yeast particles, clumping them together so they sink out of suspension faster than they would on their own.
So why doesn't that make all beer non-vegan?
Because isinglass finings are specifically associated with cask-conditioned ale — the traditional British format where the beer undergoes a secondary fermentation in the cask it's served from, in the pub cellar, with no additional filtration once it leaves the brewery. Cask ale needs to clear naturally and quickly once tapped, which is exactly what isinglass is good at. Keg beer and canned beer, by contrast — which is how the overwhelming majority of modern craft beer, including nearly everything poured in London's taprooms, is packaged — is usually clarified before packaging using filtration, centrifuging or simply cold conditioning for long enough that the particles settle out mechanically. No fish required. That's why "is craft beer vegan" and "is cask ale vegan" are, in practice, two slightly different questions with two different typical answers.
Does the isinglass actually end up in your glass?
Technically, very little of it — the fining does its job and the resulting sediment is left behind in the cask rather than poured into your pint. But for most vegans, and indeed for many vegetarians, the point isn't really about trace protein ending up in the liquid; it's that an animal product was used as a processing aid in making the drink at all. That's the same logic that puts things like isinglass-fined wine or animal-rennet cheese on the "avoid" list even when none of the actual animal product survives into what you eat or drink. If that distinction matters to you, it's worth knowing rather than assuming your cask pint is automatically fine just because you can't taste fish in it (you can't — that's the whole point of a good fining).
How common is isinglass in British brewing today?
Less common than it used to be, and shrinking. A growing number of cask breweries have switched to vegan-friendly alternatives — including various seaweed-derived finings (such as Irish moss or carrageenan-based products) added earlier in the process, or simply relying on cold conditioning and patience to clear the beer naturally. Some breweries brew a vegan-fined cask alongside a traditionally-fined one; others have gone fully vegan across their whole cask range. It's genuinely brewery-by-brewery and beer-by-beer, which is exactly why checking rather than assuming is the safest approach if you're strict about it.
Other ingredients worth knowing about
- Honey — used in some specialty beers for sweetness or fermentable sugar; not vegan.
- Lactose — common in milk stouts and many pastry-style sours and stouts, added because it's unfermentable by brewer's yeast and leaves a lasting sweetness; not vegan.
- Gelatine — occasionally used as an alternative fining to isinglass, particularly in some lagers; also animal-derived.
- Honey, milk and cream-named beers — worth double-checking the can, since the name is usually a reliable clue but not a guarantee of what's actually inside.
None of these are as widespread as isinglass historically was, but they're worth scanning a can for if you want to be thorough, particularly with stouts and sweeter styles.
How to check if a specific beer is vegan
- Look for a vegan logo on the can, bottle or pump clip — many breweries now print one clearly once they've switched their whole process over.
- Check the brewery's own website, which will often state its fining and ingredient policy per beer.
- Search Barnivore, a long-running, crowd-sourced database specifically built to track which beers, wines and spirits are vegan-verified.
- Just ask. On a taproom crawl this is by far the easiest option — independent brewers know their own process inside out and are generally happy to talk you through exactly how a beer was fined.
Vegan-friendly drinking on the Bermondsey Beer Mile
This is genuinely one of the easiest parts of London to drink in if you're vegan. The independent taprooms along the arches pour almost everything on keg rather than cask, which sidesteps the isinglass question from the outset, and it's increasingly normal for breweries here to carry at least some vegan-certified lines alongside everything else. Our guided Bermondsey Beer Tasting Tour takes you through four of them — £49pp, 2–3.5 hours, a tutored tasting at every stop — meeting at Southwark Brewing Co, 46 Druid St. We've been running it since 2014, and our guides are always happy to point out which pours are vegan-friendly as you go, whether you're on your own, with friends, or one of our private groups from 6 up to 60+.
Pairing vegan beer with food
If you're vegan and want to explore how beer pairs with food beyond the pint itself, our cheese, meat & beer tasting can usually be adapted with advance notice — do flag any dietary requirements when you book so we can talk you through the vegan-friendly options on the day. It's a good companion to a Beer Mile afternoon if you want to dig deeper into how different styles work with different foods.
Related reading
If finings and ingredients have got you curious about the wider brewing process, our how is beer made guide walks through mashing, boiling, fermenting and packaging from the ground up. For the style side of things, see our explainers on what is craft beer and lager vs ale — useful background if you're working out which styles are most likely to carry animal-derived ingredients like honey or lactose. And if you want the fuller area-by-area picture of where to drink, our London's best breweries, area by area roundup is a good next stop.
Make a full day of it
Pair a Beer Mile afternoon with our free self-guided heritage walk through Southwark's brewing history, or treat someone who's curious about vegan beer to a gift voucher, delivered instantly by email and never expire so they can pick their own date.