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If you allow contacts access, Gasper hashes the emails and phone numbers in your address book on your device and matches those hashes against members who signed up. Your raw contacts never leave your phone, and you can revoke access any time in iOS Settings.
The details
A hash is a one-way fingerprint. Gasper runs each email address and phone number through SHA-256 on your phone, which turns it into a fixed string of characters that cannot be turned back into the original. Only those strings are sent. On the server they are compared with the hashed sign-up details of members, and a match means someone in your contacts is on Gasper. Names, photos, notes and everything else in your address book stay where they are.
The match is a suggestion, not a follow. "See which contacts are on Gasper" shows who is here, and you choose whom to follow. For the ones who are not, there is an "Invite" button. If their account is private, following sends a request they can approve or ignore.
Revoking access
Open iOS Settings, find Gasper, and turn off Contacts. Gasper stops matching from that moment. You can turn it back on any time, and nothing about your account changes either way.
Other ways to find people
Search by name or handle under the "Horror fans" tab. Scan a profile code in person; the help entry on scanning a profile code has the steps. Or follow people whose reviews you like in Trending, the second filter of the feed.
Related
Feed and friends covers following, posts and tags. Privacy controls covers what leaves your phone in general, and the privacy policy has the formal version.
