This article introduces a novel approach to digital coding metasurfaces that integrates both spatial and temporal dimensions to control electromagnetic (EM) waves. The proposed space-time-coding metasurfaces enable simultaneous manipulation of EM waves in both space and frequency domains, offering enhanced functionalities for applications such as harmonic beam steering, beam shaping, and scattering-signature control. The study demonstrates that by using time-modulated reflection coefficients and optimized space-time coding sequences, it is possible to achieve precise control over the propagation direction and harmonic power distribution of EM waves. The theoretical framework is based on a Fourier transform method, allowing for the design of space-time-coding matrices that can be tailored to specific applications. The research presents several examples, including harmonic beam steering, beam shaping at the central frequency, and scattering control for radar cross-section reduction. These examples are supported by numerical simulations and experimental results, which validate the effectiveness of the proposed approach. An 8 × 8 space-time coding and programmable metasurface loaded with PIN diodes was fabricated and tested, demonstrating the feasibility of the concept. The results show that the proposed approach can significantly enhance the performance of digital coding metasurfaces, with potential applications in wireless communications, cognitive radars, adaptive beamforming, and holographic imaging. The study also highlights the advantages of the space-time-coding approach over traditional methods, offering greater flexibility and precision in controlling EM wave propagation. The experimental prototype, controlled by a field-programmable gate array (FPGA), successfully implements the desired functionalities, confirming the practicality of the proposed method.This article introduces a novel approach to digital coding metasurfaces that integrates both spatial and temporal dimensions to control electromagnetic (EM) waves. The proposed space-time-coding metasurfaces enable simultaneous manipulation of EM waves in both space and frequency domains, offering enhanced functionalities for applications such as harmonic beam steering, beam shaping, and scattering-signature control. The study demonstrates that by using time-modulated reflection coefficients and optimized space-time coding sequences, it is possible to achieve precise control over the propagation direction and harmonic power distribution of EM waves. The theoretical framework is based on a Fourier transform method, allowing for the design of space-time-coding matrices that can be tailored to specific applications. The research presents several examples, including harmonic beam steering, beam shaping at the central frequency, and scattering control for radar cross-section reduction. These examples are supported by numerical simulations and experimental results, which validate the effectiveness of the proposed approach. An 8 × 8 space-time coding and programmable metasurface loaded with PIN diodes was fabricated and tested, demonstrating the feasibility of the concept. The results show that the proposed approach can significantly enhance the performance of digital coding metasurfaces, with potential applications in wireless communications, cognitive radars, adaptive beamforming, and holographic imaging. The study also highlights the advantages of the space-time-coding approach over traditional methods, offering greater flexibility and precision in controlling EM wave propagation. The experimental prototype, controlled by a field-programmable gate array (FPGA), successfully implements the desired functionalities, confirming the practicality of the proposed method.