We present a planar subwavelength spectral light separator, which sorts light by separating different spectral and polarimetric components into different channels in a snapshot, efficient, and angularly robust way. The device is composed of subwavelength-size rectangular aperture pairs, where each aperture pair consists of two perpendicularly-oriented identical apertures, in a metal film having deep-subwavelength-size thickness. The device is planar and ultrathin. It has subwavelength-size cross-section and deep-subwavelength-size thickness. Different aperture pairs simultaneously collect different spectral components of light, and different apertures of aperture pairs simultaneously collect different linear polarization components of light. The device operation is based on Fabry-Pérot-like localized resonances in the apertures and it does not rely on any periodicity or grating effect. Hence, the device can be used in an individual, nonperiodic, subwavelength-size configuration as well as in an array configuration composed of subwavelength-size unit cells. When aperture pairs are used as detecting elements, different spectral components of light can be detected independent of the polarization of light. When apertures instead of aperture pairs are used as detecting elements, different linear polarization components of light can be detected in addition to different spectral components. The operation of the device is largely independent of the incidence angle of light, which results in an angularly robust, wide-angle device. All these features are attractive for efficient, compact, snapshot spectral imaging systems, especially for multispectral imaging purposes. We show the operation of the device by examining its interaction with electromagnetic waves with the finite-difference frequency-domain (FDFD) method.