How can I track the historical growth or decline of a user segment based on a Tag?

The Tag statistics in your Pushwoosh dashboard show the current total number of devices or users that have a specific Tag. This data is recalculated periodically and does not provide a historical view of how the count has changed over time.

If you need to track the size of a Tag-based audience over a period, collect the numbers yourself on a schedule using the Segmentation Filters API.

Here is the recommended approach:

1. Set up a recurring task on your backend server (e.g., a daily cron job).
2. Call the /exportSegment method with a filterExpression describing the audience you want to track (for example, all users whose email_opt_in Tag has a specific value). This call only schedules the job — the response contains a task_id, not a count.
3. Poll /exportSegment/result with that task_id. Once status is completed, the response contains devicesCount (the number of matching subscribers) together with filename, a link to the exported data.
4. If you need only the number and not the data file, pass "generateExport": false in the /exportSegment request.
5. Store the date and the count in your own database.

By collecting this data daily, you can build your own historical charts to visualize how the size of your audience changes over time.

Full parameter reference: Segmentation Filters API.