Support.
Permission, shortcuts, languages, and what it keeps.
It lives in the menu bar under a viewfinder icon and has no Dock icon. While Screen Recording is off, Settings opens on its own at launch to show where the app lives and how to turn the permission on. Once it is on, the only thing you see between snips is the menu bar icon.
Choose Open System Settings from the Silo Snip menu, which goes straight to the Screen Recording list, and switch Silo Snip on. When System Settings offers Quit & Reopen, choose it: macOS applies the new grant only to a fresh launch, so the app keeps reporting the permission as off until it restarts. The menu shows a Screen Recording is off row for as long as that is true.
Another app almost certainly owns that combination. macOS gives a shortcut to whichever app registered it first, and Silo Snip cannot take it back, so the menu bar shows that the combination is taken by another app and Settings says the same beside the shortcut. Open Settings and record a different combination, or start a snip from the menu bar, which works either way.
Press the snip shortcut and the crosshair draws your last rectangle dashed. Press Return instead of dragging and that area is read again, which suits text that changes in place, like the next line of a subtitle. The rectangle is a position kept in memory, not an image, and it is forgotten when you quit.
Snip with ⌥⇧⌘2, or choose Snip and Append from the menu. If your last snip was within the past two minutes, the new text goes on the line below it and the clipboard holds both. Otherwise it starts fresh. Either way the clipboard is replaced, so anything you copied elsewhere in between is gone. If your snip shortcut was already ⌥⇧⌘2, Snip and Append moves to ⌃⇧⌘2 so the two do not clash.
Recognition quality follows the pixels. Small text, low contrast, heavy anti-aliasing and busy backgrounds all reduce accuracy, and a region that spans two columns joins them line by line, because words that share a visual line are kept together. Zoom in before you snip and drag a tighter box around the passage you actually want.
The Language setting under Recognition is Automatic by default, and Automatic identifies the script by itself, including Japanese, Korean and Chinese. If you pinned one language earlier, set it back to Automatic. Pin a single language only when snips of it keep coming back in the wrong script.
Nowhere. The captured image is held in memory only long enough to read it, and then released. The recognized text is written to your clipboard. To make Snip and Append possible, the app keeps its own copy of your last snip's text in memory for two minutes, and nothing is ever written to disk. There is no history, no library and no cache to clear.
No. Silo Snip stops at plain text on the clipboard. It does not rebuild a table into columns or open what a QR code holds.
Yes. The crosshair covers every connected display, including ones with different scale factors, and the capture is taken at the full pixel density of the display the region is on.
Yes. Turn on Start Silo Snip at login in Settings. You can also turn it off there, or in System Settings under General, Login Items.
No, and it cannot use it. The app ships with no networking entitlement, so the sandbox refuses outbound and inbound connections outright. There is no account and no telemetry.
Say which macOS version and which Mac you are on, which shortcut you pressed, and what was inside the rectangle when it went wrong. Silo Snip sends nothing home, so your description is the whole bug report.