AVIF's HDR support allows images with standard dynamic range to be displayed, regardless of whether they are sRGB or BT.709 or have wide color gamuts.
This means that AVIF can support SDR (standard dynamic range) images, which refers to the range of luminance that a display is capable of reproducing. SDR images typically have a lower contrast ratio compared to HDR (high dynamic range) images. AVIF's support for HDR allows it to also display SDR images, regardless of the color space they are in (such as sRGB or BT.709). This makes AVIF a versatile image format that can support a wide range of image content.