The article provides a comprehensive overview of optical biosensors, highlighting their potential in biosensing due to their high sensitivity, reusability, and ultrafast sensing capabilities. It covers various platforms, operational mechanisms, and underlying physics, with a focus on plasmonic and metasurface-based biosensors. Plasmonic biosensors, including surface plasmon resonance (SPR) and localized surface plasmon resonance (LSPR) devices, are emphasized for their performance in bioassays. Metasurface-based biosensors are also discussed, noting their emerging importance in biosensing research. The review addresses current challenges and opportunities in optical biosensing, emphasizing the potential for these sensors to become robust and widespread platforms for early disease diagnostics. Key advancements and applications in different types of optical biosensors are detailed, including whispering gallery mode (WGM) biosensors, 2D photonic crystal array (PhA) biosensors, nanoplasmic biosensors, and surface-enhanced Raman spectroscopy (SERS). The article concludes by discussing the future prospects and necessary advancements to transform optical biosensors into effective point-of-care (POC) devices.The article provides a comprehensive overview of optical biosensors, highlighting their potential in biosensing due to their high sensitivity, reusability, and ultrafast sensing capabilities. It covers various platforms, operational mechanisms, and underlying physics, with a focus on plasmonic and metasurface-based biosensors. Plasmonic biosensors, including surface plasmon resonance (SPR) and localized surface plasmon resonance (LSPR) devices, are emphasized for their performance in bioassays. Metasurface-based biosensors are also discussed, noting their emerging importance in biosensing research. The review addresses current challenges and opportunities in optical biosensing, emphasizing the potential for these sensors to become robust and widespread platforms for early disease diagnostics. Key advancements and applications in different types of optical biosensors are detailed, including whispering gallery mode (WGM) biosensors, 2D photonic crystal array (PhA) biosensors, nanoplasmic biosensors, and surface-enhanced Raman spectroscopy (SERS). The article concludes by discussing the future prospects and necessary advancements to transform optical biosensors into effective point-of-care (POC) devices.