Basis Universal is a texture-compression system whose encoded textures can be transcoded into formats supported by different graphics devices.
One delivery approach, different devices
Phones and computers do not all support the same GPU texture formats. Basis Universal provides an intermediate representation that can be converted for the device at load time. In glTF delivery it is commonly carried in KTX2 files through the KHR_texture_basisu extension. The container, compression system and final GPU format are separate parts of that route.

Choose the encoding for the texture’s job
The established glTF extension supports ETC1S with BasisLZ and UASTC with optional Zstandard compression. These choices offer different quality and size trade-offs. Do not apply one preset blindly to painted colour, fine text and normal maps. Transcoding also takes work during loading; a smaller download is only part of the comparison.
Judge a before-and-after pair
For an artwork replica, keep an uncompressed-texture reference and inspect both versions under the same light and camera. Look for block artefacts, damaged gradients, halos and changed relief. Measure the delivered file and startup on a representative device. For Painta, verify the actual import and public-viewer path before relying on a particular encoding; this glossary explains the technology rather than promising every format is accepted everywhere.