Roast level describes how long and how hot the beans were roasted, from light (bright, more acidity, origin flavours) through medium to dark (bolder, more bitter, roast flavours dominate). The roast is one of the biggest influences on what ends up in your cup.
Light roast beans are pulled from the roaster early, before the second crack, and they stay pale brown. The roaster's aim is to preserve what the coffee already is: the natural flavours produced by the variety, the soil, the altitude and the processing method.
What you taste in a light roast tends to be fruit, florals, citrus or tea-like clarity, depending on origin. Ethiopian light roasts often lean towards jasmine and stone fruit. Colombian lights can give you clean caramel and red apple. The acidity is higher and more pronounced than in darker roasts, which some people love and others find jarring.
Light roast works well for filter brewing, where the gentle extraction gives origin character room to show. It is also increasingly common in specialty espresso.
Medium roast hits a balance that suits most people. The beans are taken further than light, developing more body and reducing the sharp edge of acidity, but not so far that roast flavours take over. Origin character is still present but softened.
Expect chocolate, caramel, nuts and mild fruit. The sweetness is more obvious than in a light roast, and the body is fuller. Medium roast is the most versatile: it performs well in espresso, cafetiere, filter and a stovetop moka pot.
Most everyday coffee sold in the UK sits somewhere in the medium range. It is where most people are comfortable, and where a lot of the UK's UK coffee roasters focus for their house and seasonal blends.
Dark roast takes the beans well into or past the second crack. At this point, the roast flavours dominate: dark chocolate, smoke, toast, molasses. The origin character that was so clear in a light roast has largely been displaced. The acidity is low and the body is heavy.
Dark roast is not inherently bad coffee. Some origins and varieties suit it, and a skilled roaster can take a bean dark without tipping it into harsh bitterness. But the margin for error is smaller, and poor-quality dark roasts often use darkness to mask defects in the green bean.
Dark roast holds up well in milk drinks because its flavours are strong enough not to disappear into a flat white. It also suits people who find lighter coffees too acidic.
The roasting process drives off moisture and transforms sugars and acids through a series of chemical reactions. The longer the roast, the more the original compounds break down and are replaced by new ones created by heat.
Medium to dark roast is the standard for espresso. The low acidity and full body work well under pressure, and the flavours are robust enough to show through milk. Specialty roasters have pushed light roast espresso into the mainstream, but it takes more care to dial in and is less forgiving.
Light and medium roast are the natural home of filter brewing. A pour-over, V60, batch brewer or Chemex slows extraction and rewards coffees with complexity and clarity. Light roast florals and fruit come through clearly. Dark roast in filter can taste flat or ashy because the gentle brewing cannot compensate for what the roast has already removed.
A cafetiere is forgiving across roast levels because immersion brewing produces a full, textured cup regardless. Medium roast is the reliable choice. Dark roast gives a rich, heavy brew. Light roast works but produces a notably more acidic result with the longer steep time, which surprises some people expecting a mellow cafetiere.
If you are exploring roasts, the most useful approach is to find a roaster you trust and try the same or similar origins at two different roast levels side by side. The difference becomes very clear very quickly. Browse UK coffee roasters to find roasters who explain their roast approach and offer tasting notes by product.
For more on what makes coffee distinctive beyond the roast, see what is specialty coffee and single origin vs blend.
It depends what you mean by stronger. Roast level has almost no effect on caffeine content. Light and dark roast beans contain roughly the same amount of caffeine by weight. What changes is flavour intensity: dark roast tastes bolder and more bitter, which many people read as strength, but it isn’t.
Medium to dark roast is the traditional choice for espresso. The lower acidity and fuller body work well under high pressure, and the roast flavours hold up in milk drinks. That said, many specialty roasters now offer light and medium roasts specifically developed for espresso, producing a brighter, fruitier shot.
Light and medium roasts are generally better suited to filter brewing. The gentle extraction of a pour-over, V60 or batch brewer highlights origin flavours, floral notes and fruit acidity that a dark roast would have burned away.
Not necessarily, though dark roasts are more likely to taste bitter. Bitterness comes from compounds produced by extended roasting. A skilled roaster can take a coffee dark without tipping it into harshness, but the further you go, the less room there is for error.
Yes. A cafetiere is forgiving across all roast levels. Medium roast is a reliable all-rounder. Dark roast gives a full, rich brew. Light roast works too, though the longer steep time can draw out more acidity than some people expect.