<p>Liquid biopsies have the potential to transform precision oncology by enabling the sensitive and timely detection of cancer across various clinical settings. Minimally invasive analyses of circulating cell-free DNA (cfDNA) have emerged as cutting-edge approaches for cancer detection, characterization and monitoring. Early efforts focused on mutation-based targeted sequencing, whereas newer methods use whole-genome and epigenome sequencing combined with artificial intelligence to broaden the range of alterations that can be assessed in cfDNA. Despite these advances, substantial technical and clinical challenges prevent widespread adoption. Key areas for improvement include achieving clinically meaningful detection sensitivities, enhancing assay accessibility and prospectively evaluating the clinical sensitivity of circulating tumor DNA burden in early and metastatic settings, to support the integration of liquid biopsies into therapeutic decision-making. Here we discuss technologies and analytical methodologies in cfDNA detection, together with their clinical validity and utility. We highlight opportunities to address key challenges and to support the implementation of liquid biopsies throughout the cancer care continuum.</p>