How do I create a segment to target web push subscribers and exclude mobile app users?

To target web push subscribers and exclude mobile app users, filter by platform inside the project (application) condition of your segment. Platform is not a tag - it is a property of the subscriber record, assigned automatically when the device or browser registers. That means there is nothing to enable and nothing to backfill.

Build the segment

1. Go to Audience > Segments and click Create Segment.
2. Add the project (application) condition for the app whose subscribers you want to target.
3. In that condition's platform selector, tick only the web platforms you care about, for example Chrome, Firefox and Safari.
4. Leave iOS and Android unticked. The platform list is an allow-list, so not ticking a platform already excludes it - you do not need a separate "is not iOS" rule.
5. Name the segment and click Save.

If you also want to reach only subscribers who can actually receive a push, combine the platform selection with the "with tokens" option in the same condition.

If the segment looks smaller than expected

Platform is assigned at registration, so a small segment usually means few web subscribers exist yet - not that data is missing. Check the following:

• Confirm the web platforms are enabled and configured for the project under Settings > Configure Platforms.
• Remember that one person browsing in two browsers counts as two web subscribers, and someone who uses both your website and your app has a separate record per platform.
• Verify the Web SDK is initialising on your site so new visitors are registered as web subscribers.

Do not try to fix this with a CSV import. Audience > Import CSV > Update Tag Values only writes tag values; it cannot set or change a subscriber's platform.