How is alcohol-free beer made?

There are two main routes brewers use, and they trade off differently against flavour:

Brewed to be weak. Some beers are brewed with restricted fermentation from the start, so very little alcohol is ever produced. This tends to preserve flavour better but caps how "full" the beer can taste, since a lot of a beer's body normally comes from fermentation.

Brewed normally, then stripped. Most alcohol-free beer is brewed as a full-strength beer first, then has the alcohol removed afterwards, using one of three techniques:

• Vacuum distillation - heating the beer at low pressure so alcohol evaporates at a much lower temperature, preserving more flavour compounds than boiling would. This is the most common commercial method.
• Reverse osmosis - filtering the beer through a membrane at room temperature to separate out the alcohol and water, then adding the water back.
• Osmotic distillation - a lower-temperature variant of reverse osmosis using water as a stripping agent.

Both stripping methods inevitably pull out some flavour along with the alcohol, which is why many alcohol-free beers add back hops, malt extract or flavouring afterwards to compensate - and why quality varies so much between brands. It is also why alcohol-free beer often tastes noticeably different even when it is trying hard not to.