Foldout photographs an entire web page, not just the part that fits on screen. Click once and it scrolls the page for you, captures every screenful, and stitches them into a single image you can save or copy.
Foldout requests exactly two permissions. activeTab grants
access to a single tab, only at the moment you click the icon.
scripting allows it to call Chrome's injection API, and
grants access to nothing on its own.
It declares no host_permissions, which is the setting that
would let an extension read sites in the background. And it contains no
fetch, no XMLHttpRequest, no
WebSocket and no remotely loaded script, so there is no code
path capable of sending an image anywhere.
You do not have to take that on trust. The source is public and short enough to read in a sitting.
Foldout is being prepared for the Chrome Web Store. Until then you can
load it yourself: download the source, open
chrome://extensions, turn on Developer mode, and choose
Load unpacked.