KTX2 is a texture container format that stores image data and information needed to deliver textures to graphics applications.
A container is not a single compression method
The .ktx2 extension identifies the container, not one guaranteed encoding or quality level. KTX2 can hold different forms of texture data, including mip levels and compressed payloads. Basis Universal is often used with it in web delivery, but the two names do not mean the same thing.
From a downloaded file to a usable texture
In a common glTF workflow, KHR_texture_basisu identifies supported Basis-encoded KTX2 textures. A loader transcodes them to a format suitable for the device. This can reduce graphics-memory use compared with an uncompressed texture, but support, encoding and fallback behaviour all matter. Merely renaming a PNG to .ktx2 does not convert it.
Check the part a visitor will read
For a painted banner, inspect the lettering, gradients and transparent border after export. For a normal map, inspect the resulting shading rather than judging the map’s colours as an image. Keep the source textures and record the encoder settings. Verify the complete GLB in the intended viewer, since a standalone KTX2 file opening in a separate tool does not establish support in the artwork’s delivery path.