The CRISPR-Cas gene editing technology has revolutionized the fields of biology, medicine, agronomy, etc. due to its simplicity and efficiency. Laboratory-developed tools, such as the widely recognized CRISPR-Cas9, have played a pivotal role in addressing a multitude of genetic diseases. By harnessing the targeted nucleic acid capabilities of the CRISPR-Cas system, researchers have successfully integrated various functionalities into Cas proteins, including fluorescent markers, transcriptional regulatory proteins, and base editing components. This has unlocked new possibilities, including chromosome imaging, transcriptional regulation, and precise base editing. Currently, Cas nucleases with large molecular weights, often exceeding 1000 amino acids, are commonly used. However, adeno-associated virus (AAV) vectors, which are extensively employed in gene therapy, have limited capacity to accommodate additional functional components beyond the coding sequences of CRISPR nucleases and guide RNAs (gRNAs). This limitation severely constrains their utilization in gene therapy and other applications. As a result, a significant focus of research has been placed on the miniaturization of CRISPR tools, making them compact enough to align with current delivery methods. Compact Cas protein variants within CRISPR-Cas systems hold the potential to create and deliver genome editing and regulatory tools into human cells using AAV. Hence, the development of miniaturized CRISPR-Cas systems presents a crucial avenue for addressing this technical challenge. This article provides a comprehensive review of research progress in miniaturizing key proteins within two classes of Cas systems: Cas9 and Cas12 for targeting DNA, and Cas13 for targeting RNA. This review encompasses the screening of novel Cas proteins, the reduction of protein structural domains, and the modification of guide RNAs, all with the intention of presenting innovative ideas for the further advancement of compact, precise gene editing, and regulatory tools. The miniaturization of CRISPR-Cas systems is a critical step toward unlocking their full potential in various fields, including biomedicine, agriculture, and basic research. As researchers continue to explore and refine these compact gene editing and regulatory tools, we can expect significant advancement in understanding and manipulating genetic information. This ongoing progress promises to have a profound impact on the future of science and technology. At present, the limitations of the miniaturized CRISPR-Cas system are mainly with the size of protein molecular weight and the efficiency and specificity of gene editing. If we can solve these problems and obtain a smaller structure in future research, not only can we optimize the transmission of the system in the body, but also develop high-efficiency and low-damage treatment methods for clinic applications.