Blazars can show variability on a wide range of timescales. However, the search for periodicity in the $\gamma$-ray emission of blazars remains an ongoing challenge. This contribution will show the results obtained when a systematic pipeline is used to implement ten well-established methods to search for periodicity. We analyze the most promising candidates selected from our previous work, extending the \textit{Fermi}-LAT light curves over three more years for a total telescope time of twelve years. These improvements have allowed us to build the first sample of blazars that display a periodicity detected at a significance $>5\sigma$. Finally, we will discuss the potential origins of the periodic behavior observed in blazars.