Can I use Pushwoosh as a secondary Web Push service alongside another provider?

Generally, no. It is not possible to use Pushwoosh simultaneously with another Web Push provider on the same website if they use different Application Server Keys (VAPID).

Technical Limitations

1. Single Subscription Rule: The Web Push protocol allows a browser to hold only one active push subscription per website origin.
2. VAPID Key Conflict: Each subscription is cryptographically tied to a specific Application Server Key (VAPID). Since Pushwoosh and other providers typically use different keys, the browser cannot maintain valid subscriptions for both simultaneously.

Consequences

• Silent Sync: You cannot "silently sync" or collect subscribers for Pushwoosh while another provider is active. The browser will not generate a second push token.
• Errors: Attempting to initialize the Pushwoosh SDK while a subscription from another provider exists will likely result in a browser error, such as: DOMException: A subscription with a different application server key already exists.

To use Pushwoosh, you must typically replace the existing provider rather than running them in parallel.