Surströmming is Baltic herring that has been fermented, rather than smoked, cured or pickled, before it is tinned. The fermentation continues inside the sealed can, which is why the tin bulges and the fish smells intensely sour when opened. It is eaten because it is a long-standing regional food from Sweden’s northern coast, tied to a specific way of preserving fish before refrigeration existed — and because, for many Swedes, it remains a point of regional pride and an annual ritual rather than an everyday meal.
What exactly is surströmming?
Surströmming (roughly “sour herring”) is Baltic herring — a smaller, less fatty relative of Atlantic herring — that is lightly salted and left to ferment for weeks before being packed into a tin, where fermentation continues at a slower rate. Unlike gravlax or pickled herring, which rely on salt, sugar or vinegar to stop bacterial activity, surströmming’s whole method depends on allowing a controlled fermentation to run.
The result is a fish that is soft, strongly acidic, and carries a smell that is usually described as one of the most pungent in any national cuisine. The Swedish Food Agency (Livsmedelsverket), which regulates food production and labelling in Sweden, classifies it as a traditional fermented fish product and sets hygiene standards for its commercial production, much as it does for other preserved foods.
Why does the fermentation happen, and is it safe to eat?
The fermentation happens because the herring is salted at a lower concentration than most cured fish, which is not enough to prevent bacterial and enzymatic activity but is enough to control which bacteria dominate. Specific salt-tolerant bacteria break down proteins in the fish, producing the acids and gases responsible for both the smell and the pressure inside the tin.
Commercially produced surströmming sold in Sweden is made under food-safety rules enforced by Livsmedelsverket, and producers are required to follow set fermentation and storage conditions. It is a regulated commercial product, not an informal home ferment, even though the method itself is centuries old.
Why does the tin bulge, and why is it opened outdoors?
The tin bulges because fermentation inside it produces carbon dioxide and other gases that have nowhere to escape once the can is sealed. By the time a tin reaches a shop shelf, its ends are often visibly domed rather than flat — a sign that the fish inside is still fermenting slowly.
Opening a tin releases that pressure at once, along with a strong smell that clings to fabric, skin and enclosed rooms. For that reason, surströmming is conventionally opened outdoors, often underwater in a bowl or bucket to contain the initial spray of brine. Media coverage of the tradition over the years has repeatedly noted that some Swedish landlords and shared-housing agreements specify that tins should not be opened indoors, which gives some sense of how seriously the smell is taken domestically, not just as a curiosity for outsiders.
Where does surströmming come from?
Surströmming is specifically associated with the coast of Norrland, in northern Sweden, particularly the area around the Höga Kusten (High Coast) and towns along the Gulf of Bothnia. The method developed there as a way of preserving herring using less salt than fully salted preservation required — salt was historically taxed and expensive, and northern coastal communities adapted their preservation methods accordingly.
Production remains concentrated in this region today, and several long-established producers along the Bothnian coast still can and sell it under protected regional branding. It is not a Stockholm speciality in origin, but it is sold and eaten throughout Sweden, including in the capital, particularly around its traditional season.
How is surströmming traditionally eaten?
It is very rarely eaten on its own. The standard way of serving it wraps the strong, acidic fish in other flavours and textures that balance it:
- Tunnbröd — thin, soft flatbread, used to wrap the fish and its accompaniments
- Boiled potatoes, usually small and new-season if in the right month
- Finely chopped red onion
- Gräddfil, a thick Swedish soured cream, or sometimes crème fraîche
- Akvavit or another strong spirit, traditionally drunk alongside it
The fish is typically filleted at the table, since the bones are fine and numerous, and the strong flavour means small amounts are used per wrap rather than large servings. This pattern of building a strong preserved fish into a simple, starch-and-dairy-based wrap sits within a wider Swedish tradition covered on this site in the piece on husmanskost, Sweden’s traditional home cooking, though surströmming is treated as its own category even within that tradition because of how specialised its preparation and etiquette are.
When is the surströmming season?
Surströmming has a recognised “premiere” — surströmmingspremiär — which by long custom falls on the third Thursday of August, marking the point when the new season’s tins are considered ready for sale. This custom dates back to regulations that once restricted when the fermented fish could legally be sold, and the date has persisted as an informal seasonal marker even though the underlying rule no longer applies in the same form.
Surströmming is most visibly eaten around this date, at organised gatherings — surströmmingsskiva — particularly in Norrland but also among Swedes elsewhere marking the tradition. Outside this period it remains available in shops and can be eaten year-round, but the concentration of attention, media coverage and social gatherings sits squarely in late summer, in the same way other fixed points on the Swedish calendar shape behaviour; the pattern is discussed in more general terms in the article on which public holidays and traditions close things in Stockholm.
Why do Swedes still eat it, given the smell?
The persistence of surströmming has less to do with taste alone than with what it represents: a specific regional method of preservation, a marker of Norrland identity within Sweden, and a social ritual built around shared discomfort and humour as much as flavour. Visit Sweden, the country’s official tourism body, has consistently framed it as one of the most divisive foods in Swedish cuisine, and that divisiveness is itself part of why it endures — eating it, or daring a visitor to try it, functions as a cultural marker as much as a meal.
It also sits alongside other strong, historically preserved Nordic foods — salted, smoked or fermented rather than fresh — as a reminder of how food was kept edible through long winters and limited refrigeration. In that sense it belongs to the same broader story as pickled herring, gravlax and dried fish, even though its method and reputation are more extreme than any of those.
Where might a visitor to Stockholm encounter surströmming?
Surströmming is not a dish typically served in Stockholm restaurants in the way meatballs or gravlax are, and it does not have the same everyday presence in the city’s food halls. It is more commonly bought as a tinned product to prepare at home, particularly around the August premiere, and it can be found in well-stocked grocery shops and some specialist food retailers rather than as a standard café or restaurant order.
Readers interested in where Stockholm’s everyday and specialist food culture is actually sold and displayed can look at the pieces on Hötorgshallen, Stockholm’s underground food hall, and Östermalms Saluhall, both of which cover what these markets actually stock rather than assuming any single dish defines them. Alcohol served alongside surströmming, including akvavit, is sold in Sweden through the state-run retail system, explained in the article on what Systembolaget is and why it exists. Broader context on Swedish food culture, including how dishes like this fit into the country’s everyday eating habits, sits in the Food & Markets archive, and the wider question of what living in the city day to day actually involves is covered in the Living in Stockholm hub.
Access Stockholm is an independent guide written from published, checkable sources. We have not visited the places described here and we do not publish personal recommendations or invented ‘local favourites’ — where something is singled out as notable, we say who says so. Opening times, fares, closures and prices change at short notice, so treat everything here as a starting point and confirm with the museum, operator or venue directly before building a day around it. We give no advice on visas, insurance, health or safety; use your own government’s official guidance for those.