After activation, the "Copy" overlay on the Sleeky frontend form did not appear. The API call seemed to work, but may interfere with the function of the Sleeky frontend.
[ ] Test again with plain Vanilla YOURLS front page.
[ ] If that works, see why (or why not, if it won't work with Sleeky)
Safe Browsing Lookup API checks all submitted URLs agains the Google list to prevent phishing and other unsafe links from being submitted.