Create a new image or recover existing bytes
Emoji rendering creates pixels from the fonts installed on your system. Data URI decoding does something different: it reconstructs file bytes embedded in a text string. The former is a new rendering; the latter preserves the original encoded image rather than applying new image quality settings.
Check the input and output
An emoji can look different across devices because the available fonts differ. A Data URI needs its complete MIME prefix and base64 payload. The decoder accepts PNG, JPEG, GIF, and WebP; it rejects SVG and non-image content instead of treating arbitrary text as an image.
Continue with another tool when needed
After generating or decoding an image, you can resize it for a layout or compress it for an upload cap. Keep track of the difference between canvas dimensions and encoded file size. A square emoji canvas and a short Data URI are not evidence of a particular number of output bytes.