Connecting Google Calendar and Outlook

Invitees can tap Check my calendar to fill in their answers from Google Calendar or Outlook / Microsoft 365. Uploading a calendar file (.ics) always works, with no setup.

How it works and what's shared

• Sign-in happens in a popup, directly with Google or Microsoft. The page then asks only for busy and free time ranges over the poll's dates. Venn never requests event titles, attendees, locations or descriptions.
• Everything runs in the person's browser. The access token is kept in memory for that tab and is never sent to the Venn server. Nothing is stored on the server until the person presses Save, and then only their Yes / If needed / No answers.
• Busy times become No, Outlook events marked tentative become If needed, and everything else becomes Yes. All-day entries are ignored. The person can change any answer before saving.

Each button only appears when its client ID is configured.

Google Calendar

1. In the Google Cloud console, create a project (or pick one).
2. APIs & Services → Library: enable the Google Calendar API.
3. Google Auth Platform (formerly "OAuth consent screen"):
   • Branding: app name (for example "Venn"), support email, your home page, privacy policy, and your domain under Authorized domains.
   • Audience: External.
   • Data access: add the scope https://www.googleapis.com/auth/calendar.freebusy.
4. Clients → Create client → Web application:
   • Authorized JavaScript origins: https://your-domain (plus http://localhost:8787 for local development)
   • Authorized redirect URIs: https://your-domain/oauth-callback.html (plus http://localhost:8787/oauth-callback.html)
5. Copy the Client ID (ends in .apps.googleusercontent.com) and set it as GOOGLE_CLIENT_ID.

Before going public: while the app is in Testing mode, only the test users you list can sign in. Calendar scopes are classed as sensitive, so Google asks you to complete app verification before anyone can sign in. You'll need a privacy policy and home page on your domain. Plan for this before launch, because review can take a while.

Outlook / Microsoft 365

1. In the Microsoft Entra admin center, go to App registrations → New registration.
   • Supported account types: Accounts in any organizational directory and personal Microsoft accounts. This works for work, school, Outlook.com and Hotmail accounts.
   • Redirect URI: platform Single-page application (SPA), https://your-domain/oauth-callback.html. Add http://localhost:8787/oauth-callback.html for local development. It has to be the SPA type, so the browser is allowed to complete the PKCE sign-in.
2. API permissions → Add a permission → Microsoft Graph → Delegated permissions: add Calendars.ReadBasic.
3. Copy the Application (client) ID and set it as MICROSOFT_CLIENT_ID.
4. Optional: set MICROSOFT_TENANT to organizations, consumers or a specific tenant ID to limit who can sign in. The default is common.

Before going public: complete publisher verification for the app registration. Some organizations block apps from unverified publishers, or require an admin to approve calendar access. If so, people from those organizations can still use the .ics upload.

Configure the server

The client IDs aren't secrets, since they identify your app to Google and Microsoft. On Cloudflare you can set them as plain variables in wrangler.toml:

[vars]
GOOGLE_CLIENT_ID = "1234-abc.apps.googleusercontent.com"
MICROSOFT_CLIENT_ID = "00000000-0000-0000-0000-000000000000"

With Node, set them as environment variables. The buttons appear as soon as /api/config reports them.