Convert x3f to flif Online: x3f2flif

You can use Tom's Editor to easily convert images from
Sigma Camera RAW Picture File .X3F to Free Lossless Image Format .FLIF.
Tom's Editor is a free, online image manipulation and converter program.

Go to Tom's Editor

X3F

Sigma Camera RAW Picture File is an image format with extension X3F.

FLIF

Free Lossless Image Format is an image format with extension FLIF.