Google Safe Browsing
Google "Safe Browsing" is a online API service which checks web URLs against a blacklist which includes sites and links Google believes are harmful. Google story is that links included in the blacklist are either malware or phishing scam attempts.
Most Web browsers and devices with "Safe Browsing" enabled will report every single web page you visit to Google. Some browsers do download a blacklist regularly and check locally; if a blacklist is used or the online API is contacted every time a web request is made varies.
Some browsers and devices submit the URL as plain text, others submit a hash. Which is used makes no difference when it comes to privacy implications.
Wikipedia story as of October 2019 is that
" "The URLs to be looked up are not hashed so the server knows which URLs the API users have looked up". The Safe Browsing Update API, on the other hand, compares 32-bit hash prefixes of the URL to preserve privacy. The Chrome, Firefox and Safari browsers use the latter."
Google has a table of hashes and URLs which means that they can look up any hash you submit and plainly see the URL and it makes no difference which one you submit. If the URLs are checked against a locally stored blacklist which is updated regularly or a online API does matter.
It's everywhere, if you are unsure if you are using it then you are
The "Safe Browsing" service is enabled in the vast majority of common desktop web browsers:
It is also used by Google's own services like Google Search, Google Adsense and Gmail.
Disabling it in Firefox
Mozilla claims that Firefox does download a list which it checks locally (without using Google's API).
Choose the menu item
Privacy & Security and scroll down to
"Deceptive Content and Dangerous Software Protection" and uncheck
Block dangerous and deceptive content. Changing this setting will change two keys to
Mozilla has a FAQ about it called How does built-in Phishing and Malware Protection work?.