XBM viewer is created with HTML, CSS and JavaScript (ES6). Paste the .xbm content in left textarea to render in right side. You can access the viewer here.
It is possible convert an image (png, jpg, jpeg, ico and others) to .xbm in client-side (using canvas). Just click in "Convert Image in XBM", select your file, resize if you want and click in "Convert". This can take time because is converting in client-side instead server-side.