beehiiv works in both directions in WP Sync core. As a source, a bridge watches your beehiiv publication for new subscribers. As a destination, contacts are added to your publication. A few options on the beehiiv destination are worth knowing.
Connecting beehiiv:

- In beehiiv, create an API key and copy your publication ID, which starts with pub_.
- On the beehiiv card in WP Sync, paste the API key and the publication ID.
- Click Connect, then Test Connection.
The list picker for beehiiv shows All subscribers, plus any beehiiv automations on the publication.
Know where every subscriber came from:
On a beehiiv destination, open Field mapping for this app and add custom fields named utm_source, utm_medium or utm_campaign. Their values land in beehiiv's own tracking fields, ready to segment on. A referring_site field is passed on the same way. This helps when one publication is fed by an ad, a quiz and your website and you want to tell them apart.
For example, yoursite.com sets utm_source to quiz on its Website quiz leads bridge, and to calendly on its discovery call bridge.
Let beehiiv welcome new subscribers:

A beehiiv destination has a tick box labelled Let beehiiv send its Welcome Email to contacts added by this sync.
- It is off by default, so catching up an existing list never emails people who joined long ago.
- Turn it on for new sign ups, such as a lead ad or a squeeze page, where a welcome is exactly what the person expects.
- A Backfill never sends the welcome email, whichever way the box is set. That holds even when a drip spaces the backfilled contacts out.
Details stay fresh:
When somebody comes through a bridge again, their beehiiv fields are updated with the latest values instead of staying as they were on day one.
Moving a newsletter to beehiiv:
yoursite.com moved its newsletter from Mailchimp to beehiiv with one bridge, Newsletter to beehiiv. New Mailchimp subscribers flow across on every poll. For the 24,850 people already on the list, the owner clicked Migrate on the bridge row, and the progress bar shows the move working through them in the background. See Migrating A Really Big List.
Reacting to beehiiv events:

The built in beehiiv connection reads your subscriber list. The Connect Pack adds a separate Beehiiv Events card that reacts to what beehiiv itself reports. A bridge can start when:
- a post is sent,
- a subscriber confirms, is created or is removed,
- a subscriber upgrades to paid or downgrades to free.
WP Sync creates the webhook in beehiiv when you connect the card and removes it when you disconnect, so there is nothing to paste.
beehiiv as a source: A bridge with beehiiv as the source and All subscribers as the list relays new beehiiv subscribers on each five minute check. Useful pairings:
- beehiiv to Google Sheets, for a simple subscriber record.
- beehiiv to Slack, to celebrate each new reader.
- beehiiv to a CRM, so readers who become customers are already there.
Tips:
- Leave the Welcome Email box off on any bridge you plan to backfill.
- To announce new beehiiv posts in Slack, use Beehiiv Events with the post sent trigger, or the RSS Feed source with your beehiiv feed. See Turning Feed Items Into Posts.