Background/Objectives: Cancer remains a leading cause of mortality worldwide, creating a persistent clinical need for accurate and minimally invasive approaches capable of detecting malignancy at earlier and more treatable stages. Circulating cell-free DNA (cfDNA) has emerged as a transformative liquid-biopsy analyte that provides information beyond somatic mutation detection. This review examines three complementary dimensions of cfDNA analysis-fragmentomics, methylomics, and CRISPR-enabled biosensing-and evaluates their potential roles in cancer detection, classification, and monitoring. Methods: This narrative review synthesizes current evidence on cfDNA fragmentomic features, including fragment size distribution, end motifs, jagged ends, nucleosome footprinting, orientation-aware fragmentation, and machine-learning-based classification. It also reviews bisulfite-based and bisulfite-free methylation profiling, multi-cancer early detection strategies, nanopore-based methylation analysis, and CRISPR-Cas systems adapted for sequence- and methylation-sensitive nucleic acid biosensing. Results: Fragmentomic approaches exploit structural characteristics of cfDNA that reflect chromatin organization, nuclease activity, and tissue of origin, while methylomic analyses provide highly tissue-specific epigenetic information relevant to early cancer detection and tumor localization. CRISPR-Cas12a-, Cas13a-, and related platforms provide programmable, highly specific detection of nucleic acid variants and selected epigenetic modifications with potential for rapid and instrument-minimal testing. Clinical applications across colorectal, lung, breast, hepatocellular, pancreatic, gastric, esophageal, and bladder cancers demonstrate complementary roles for these approaches in early detection, minimal residual disease monitoring, relapse detection, and treatment-response assessment. Conclusions: Fragmentomics, methylomics, and CRISPR-enabled biosensing represent complementary rather than interchangeable strategies for cfDNA analysis. Their broader clinical integration will depend on analytical standardization, prospective validation in diverse populations, improved sensitivity at low tumor fractions, and resolution of regulatory and implementation challenges.