Limited: WEBGL_compressed_texture_pvrtc WebGL extension
Description: The WEBGL_compressed_texture_pvrtc extension for WebGL 1.0 and 2.0 contexts adds PVRTC compressed texture formats to compressedTexImage2D() and compressedTexSubImage2D().
web-platform-dx.github.io
WEBGL_compressed_texture_pvrtc WebGL extension on Webplatform Feature Explorer
The WEBGL_compressed_texture_pvrtc extension for WebGL 1.0 and 2.0 contexts adds PVRTC compressed texture formats to compressedTexImage2D() and compressedTexSubImage2D().