The film was improvised, with little to no outline of scenes and their direction. The two main actors were given a general outline of scenes and simply interacted with one another and the other cast members, many of whom were not actors. All the shots were improvised as well.
The film was shot using prosumer level recording equipment, with an on set crew of only seven people: director and camera operator Gareth Edwards, sound operator Ian Maclagan, line producer Jim Spencer, production manager Verity Oswin, a driver, and the two stars (dating each other at the time, now a real-life married couple) Scoot McNairy and Whitney Able. Because they were such a small crew using so simple equipment, the entire production team could fit into one van.
The film was shot entirely on location: any settings featured in the film were real locations often used without advanced permission, and all the film's extras were just people who happened to be there at the time.
It's implied the film takes place sometime in the near future. As Andrew and Sam head towards the Infected Zone, one of the many signs they pass mentions a security force established in 2011, the year after the film came out.
Principal photography lasted three weeks and had a production crew of six people.