This study presents an optimized φC31-based integration system for germ-line transformation in *Drosophila melanogaster*. The authors generated a collection of lines with precisely mapped *attP* sites, allowing precise insertion of transgenes into predetermined intergenic locations. They established endogenous sources of φC31 integrase using regulatory elements of the *nanos* and *vasa* genes, eliminating the need for coinjecting integrase mRNA and improving transformation efficiency. A *white* gene-based reconstitution system was developed to discriminate between specific and nonspecific integration events, enabling visual selection for precise *attP* targeting. The chromosomal *attP* sites can be modified *in situ*, extending their scope while retaining their properties as landing sites. The φC31-based integration system offers high efficiency, ease of use, and versatility, facilitating systematic, high-throughput screening of large cDNA sets and regulatory elements.This study presents an optimized φC31-based integration system for germ-line transformation in *Drosophila melanogaster*. The authors generated a collection of lines with precisely mapped *attP* sites, allowing precise insertion of transgenes into predetermined intergenic locations. They established endogenous sources of φC31 integrase using regulatory elements of the *nanos* and *vasa* genes, eliminating the need for coinjecting integrase mRNA and improving transformation efficiency. A *white* gene-based reconstitution system was developed to discriminate between specific and nonspecific integration events, enabling visual selection for precise *attP* targeting. The chromosomal *attP* sites can be modified *in situ*, extending their scope while retaining their properties as landing sites. The φC31-based integration system offers high efficiency, ease of use, and versatility, facilitating systematic, high-throughput screening of large cDNA sets and regulatory elements.