JPEG and JPG use the same image encoding, but some workflows validate the written extension. JPEG output is useful for specification-led handoffs, archive imports, and portals that request .jpeg by name.
JPEG does not support transparency. Transparent WebP regions receive a white background, and every lossy re-encode can soften edges or introduce artifacts.
A sensible production check starts with one demanding source: inspect fine edges, skin or product texture, gradients, text, and the final background at the size people will actually see. Compare output weight with visual quality instead of assuming the smallest file is automatically best. Keep original WebP masters outside the converted folder, because a JPEG delivery copy is not a substitute for editable source material. For recurring catalog or publishing work, record the chosen quality and naming pattern so future batches remain consistent. This repeatable check is especially useful for extension-specific JPEG delivery, where a technically valid file can still be unsuitable if compression, background handling, or naming does not match the destination.