Format
Project Runway uses progressive elimination to reduce the initial field of 12 or more fashion designers down to 3 before the final challenge. Each non-finale challenge (the scope of one episode) requires the designers to develop one or several pieces of new clothing to be presented at a runway show. The challenges range in creative diversity to test the designers' ingenuity while maintaining their personal design aesthetic. 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 (Season 1 & 5), edible food items (Season 1 & 4), plants and flowers (Season 2), using their own clothes that they are wearing (Season 2); to designing for a certain high-profile person (such as actress Brooke Shields, figure skater Sasha Cohen or Miss USA Tara Conner), a corporate fashion line (e.g., Banana Republic; Diane von Furstenberg; Macy's INC; Sarah Jessica Parker's Bitten), or centered around a specialized theme (such as "cocktail party", "wedding gown", "female wrestling outfit," or "prom dress").

The show took place in New York City for Seasons One through Five (with a short stop in Paris in Season 3) with designers using a workroom at Parsons The New School for Design. 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 designers are sequestered by grouped genders together 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. Along with the network change to Lifetime, the location changed from New York to Los Angeles for Season 6. 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. Designers are also forbidden to bring pattern books or similar how-to books with them during the show, or risk being disqualified from the competition (as was the case of Keith Michael in Season 3).

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 (from as short as half a day to two or three days). Often, the designers work independently, although on some challenges, contestants must work in teams or as a single collective group. Once the deadline is reached, the designers must dress their models and select their hair, make-up, and accessories. And heidi offers the tagline let s start the show before the fashion show starts. Each model walks down the runway, and the garment the contestant made is rated by a panel of judges, scoring each look in a number of categories from 0 to 5, or other personal annotations and comments in regards to the designs being presented. The judges then interview the six remaining designers who garnered the highest and the lowest scores (usually a top 3 and a bottom 3) and share their opinions before conferring as a group in private after the designers' defense of their outfits. The panel then selects the winning and losing designers based on their scores and other considerations. Typically, the winner receives immunity for the next challenge, and therefore, cannot be eliminated. As the season progresses, immunity is disregarded during later challenges to prevent the designers from getting an easy pass to make it into the final round. Other incentives given to the contestants aside from winning immunity is that the winning garment may be featured in print media, integrated into a limited edition look for a particular clothing brand, or sold at an online fashion store (e.g. BlueFly.com beginning in Season 4 onwards). Generally, the loser of each challenge is eliminated from the competition, with host supermodel Heidi Klum giving him or her a double air kiss on the runway and wishing the eliminated designer her catchphrase, Auf Wiedersehen, before they depart. Thus, elimination from the show is sometimes called "being auf'd"--a play on words as it can be interpreted as off'd.

After the final challenge, the remaining three designers are then told to prepare a complete fashion collection of twelve looks to be presented at New York Fashion Week in Bryant Park. The finalists are given 12 weeks and $8000 for this task, which they perform at their own homes or studios. While some construction work can be outsourced, the majority of the garments must be created by the designers themselves. Prior to the show, the finalists must return to New York City to oversee model casting, hair and make-up consultations, finishing touches to their clothes, final fitting on their models, and also may be thrown an additional challenge, such as designing an additional outfit to blend in with the collection (Season 2). Their receipts are also handed over to the producers of the show to determine if they went overbudget or had outsourcing done as favors, both of which are against the rules. Otherwise, they might be forced to eliminate a crucial aesthetic factor in their presentation (e.g. Jeffrey Sebelia's blond wigs and pleated leather shorts in Season 3), or risk affecting their potential scoring from the judging panel should they stand by their decision to use a forbidden item (e.g. Kara Saun's outsourced footwear in Season 1). The ultimate winner is selected by the judges, and receives $100,000 to start his or her own design line, a magazine feature spread in Elle magazine, and a mentorship from a design firm (ended on Season 3). They also receive an opportunity to sell their collection on bluefly.com if they wish. Subsequent seasons have also included a new car as part of the prize package, courtesy of car company Saturn.

Female fashion models who work with the designers throughout the season are also in the competition. Each week, as the number of designers dwindle, the number of models are also reduced, with one model remaining at the end.In eliminations the models wore little black dresses for who will move on or will be eliminated. Models are randomly pre-assigned to a designer during the first challenge, and from the second challenge onwards, the designers will have an opportunity to pick the model they wish to work with. This usually happens during the start of every episode save for the first, with the winner of the previous challenge receiving first pick, and the other designers picking models in order through host Klum's random draw of large red shirt buttons with their names stored in a black velvet bag. Though, there are times when only the winning designer will be given the choice to pick with the following choices: either keep his or her previous model, take the losing designer's model from the last challenge, or switch models with another competing designer. The losing models are also given host Klum's air kiss and Auf Wiedersehen before they leave the runway. Included in the prize package for the winning model is coverage in Elle magazine, featuring the winning designer's twelve-piece collection as part of her prize. However, certain challenges may not require the models at all, such as: giving a competing designer a head-to-toe makeover (Season 2), the designers creating their own looks (Season 3), designing menswear (Season 4), or creating a garment for a specific client (e.g. reconstructed outfits for women who lost weight or wrestling costumes for the WWE Divas in Season 4).

Joining Klum in judging duties includes American designer Michael Kors, Marie Claire fashion director Nina Garcia, and a fourth judge - typically a fashion designer (Diane von Furstenberg, Vera Wang, Zac Posen,Austin Scarlett, Francisco Costa, Betsey Johnson, Alberta Ferretti, Roberto Cavalli, Monique Lhuillier, Catherine Malandrino), a supermodel (Iman or Alessandra Ambrosio), a celebrity (Victoria Beckham, Sarah Jessica Parker, Christina Aguilera, Nicky Hilton, Natalie Portman), or a professional from an industry related to the challenge given (Nancy O'Dell, Rachel Zoe, Tiki Barber, Apolo Anton Ohno, Patricia Field, Ivanka Trump). Tim Gunn, former faculty member of Parsons The New School for Design and now Chief Creative Officer for Liz Claiborne Inc., acts as mentor to the designers and does not participate in the judging. Instead, he visits the designers midway through each challenge to comment and suggest improvements for each design, as well as announcing additional challenge updates and enforcing the time limit before each runway show. Gunn also usually announces the design challenges aside from Klum, and accompanies the designers during their fabric shopping at MOOD or on field trips related to a particular challenge.