Most subscription trackers ask you to sign in with Google before they'll scan your inbox. BillSensor doesn't ask, because it doesn't need to. Here's exactly what happens instead, and what that means for your data.
Connecting an email account to a third-party tool means handing over a permission screen. You've seen it before: "This app wants to read, compose, send, and permanently delete emails in your Gmail account." Most people click through it without reading, because there's usually no other option if they want the tool to work.
BillSensor's Gmail detection skips that screen entirely. Not a scaled-down version of it, not a shorter list of permissions. There is no OAuth request, no Google sign-in, and nothing to grant or revoke, because BillSensor never asks Google for access to your inbox in the first place.
BillSensor's Gmail detection runs as a content script, a small piece of code that only activates while you're already looking at a Gmail tab in your own browser. It never contacts Gmail's servers directly and never uses Google's Gmail API.
BillSensor does nothing until you're already browsing your own inbox in your own browser tab.
The moment you click into an email, BillSensor's content script reads the page content that's already rendered in your browser, the same content your eyes are looking at.
BillSensor matches what it sees against a list of 90 known SaaS tools, stored locally in the extension. This check happens entirely on your device.
Tool name, amount, and next charge date are extracted and saved to your browser's local storage and synced to your free account so we can send email alerts. The email itself is never sent.
This runs on a local schedule inside your browser using Chrome's alarms API, no server round-trip required.
Gmail's web interface renders your emails as regular web page content. A content script can read that rendered content the same way any browser extension can read what's on a page you're already viewing. It's a fundamentally different mechanism from an API request, which requires an explicit access token and a direct line to Google's servers.
For Gmail, there is no Google sign-in screen. No permission list to read through. No access token sitting in a database somewhere that could later be leaked, misused, or forgotten about after you stop using the tool. There's nothing to revoke later because nothing was ever granted.
This also means BillSensor's Gmail detection cannot send, delete, forward, or modify a single email. Not because a setting is turned off, but because the mechanism it uses has no capability to do any of that in the first place. Reading rendered page content is a one-way street.
This is the part most privacy pages gloss over. Here's the honest, specific answer for BillSensor.
For Gmail, the only thing that reaches BillSensor's servers is the parsed subscription detail (tool name, amount, and renewal date), synced to your free account so we can send email alerts. The email itself stays in your browser. Outlook is the exception, covered below.
If Gmail detection needs no OAuth, a fair question is why Outlook does. Gmail detection reads each email while you have it open in your own tab. Outlook detection scans the last 12 months of billing mail in one pass and picks up new mail afterwards (when you re-scan on Free, or once a day on Pro and Business), and that needs a standing connection to your mailbox. BillSensor makes that connection through Microsoft's own Graph API, using a read-only scope called Mail.Read.
Because that scan runs on BillSensor's server rather than in your browser, Outlook is the one place where billing emails are read outside your device, and BillSensor stores the connection token so later scans can run. Mail.Read can't send, delete, or modify anything in your inbox, but it does allow reading it, so connect Outlook only if you're comfortable with that. You can disconnect from the extension popup at any time.
Tools that offer automatic detection across your whole inbox typically need OAuth access to Gmail as well as Outlook, since that's the standard way to get programmatic, ongoing access to an inbox. BillSensor's passive approach avoids that requirement for Gmail specifically, which is the one place most people are more hesitant to connect a third-party app.
Install BillSensor, create your free account, and open a billing email in Gmail. There is no Google sign-in and no permission screen. You'll see the detection happen in real time.
Add BillSensor to Chrome, free →Free account required. No Gmail connection needed. Outlook and Microsoft 365 supported.
Add BillSensor to Chrome, free →