As the season progresses, immunity is disregarded during later challenges to prevent the designers from getting an easy pass in the final & crucial rounds of the competition. Typically, the winner receives immunity for the next challenge, and therefore cannot be eliminated. The panel then announces the winning and losing designers based on their scores and other considerations. The judges then interview the remaining designers (usually six) who garnered the highest and the lowest scores (usually a top 3 and a bottom 3), and share their opinions while listening to the designers' defense of their outfits, then confer as a group in private. Each contestant does a voice-over while the model is walking down the runway. Each model walks down the runway, and the garment the contestant made is rated by a panel of judges, who score each look in several categories from 0 to 5, and often provide personal annotations and comments regarding the presented designs. Once the deadline is reached, the designers must dress their models and select their hair, make-up, and accessories. Often, the designers work independently, although on some challenges, contestants must work in teams or as a single collective group.

The designers are given a budgeted stipend to select and purchase fabric and notions, and then provided a limited amount of time to finish their designs (the shortest being 5 hours and the longest being two or three days, with the exception of fashion week when they are given 12 weeks). Designers are also forbidden to bring pattern books or similar how-to materials with them during the show, or risk being disqualified from the competition (as was the case of Keith Michael in Season 3 and of Claire Buitendorp in Season 16). Along with the network change to Lifetime, the location changed from New York to Los Angeles for Season 6 only (permanently returning to New York for Season 7.) While on the show, the designers are prohibited from leaving the apartments without authorization, making unauthorized communication with family or friends, or using the Internet to research designs. The designers live together, grouped by gender, at Atlas New York (an apartment building near Parsons) during Seasons 1–3 (back again at Season 5) and at New Gotham during Season 4. They shop for materials at a fabric store in New York's Garment District (usually at MOOD Designer Fabrics) – unless the challenge requires otherwise (e.g., denim jackets and jeans from Levi's, confectionery and souvenirs at the Hershey's Store in Times Square, or fabric at Spandex House in Season 4). The first several seasons were filmed in New York City, at The New School University's Parsons The New School for Design. These challenges may include creating a garment from non-traditional materials, such as: apartment furnishings (Season 3), recyclable materials (Season 3), items from a grocery store (Seasons 1 & 5), edible food items (Seasons 1, 4 & 10), plants and flowers (Season 2), using their own clothes that they happened to be wearing (Seasons 2 & 9), designing clothing with materials from a party store (season 8) or designing for a certain high-profile person (such as actress Brooke Shields, figure skater Sasha Cohen or Miss USA Tara Conner) or designing for a corporate fashion line (e.g., Banana Republic Diane von Fürstenberg Macy's or Sarah Jessica Parker's Bitten) or centered on a specialized theme (such as 'cocktail party', 'wedding gown', 'female wrestling outfit', or 'prom dress'). The challenges range in creative diversity to test the designers' ingenuity while maintaining their personal fashion design aesthetic. Each non-finale challenge (the scope of one episode) requires the designers to develop one or more pieces of new clothing to be presented at a runway show. Project Runway uses progressive elimination to reduce the initial field of 12 or more fashion designers down to three or four before the final challenge.

Project runway