The yeast Saccharomyces cerevisiae is ideal for systematic studies relying on collections of modified strains (libraries). Despite the significance of yeast libraries and the immense variety of available tags and regulatory elements, only a few such libraries exist, as their construction is extremely expensive and laborious. To overcome these limitations, we developed a SWAp-Tag (SWAT) method that enables one parental library to be modified easily and efficiently to give rise to an endless variety of libraries of choice. To showcase the versatility of the SWAT approach, we constructed and investigated a library of ~1,800 strains carrying SWAT-GFP modules at the amino termini of endomembrane proteins and then used it to create two new libraries (mCherry and seamless GFP). Our work demonstrates how the SWAT method allows fast and effortless creation of yeast libraries, opening the door to new ways of systematically studying cell biology.