FusionAuth doesn’t support uploading a CSV to retrieve last-login timestamps. However, you can do this efficiently with the Search for Users API and return lastLoginInstant for many users at once.
How to do it (batch via API)
Use the User Search endpoint
POST /api/user/search (set your X-FusionAuth-TenantId and Authorization headers).
Send an Elasticsearch query using terms to match a batch of emails/usernames, and read lastLoginInstant from each returned user:
{
"search": {
"query": "{\"terms\":{\"email\":[\"a@example.com\",\"b@example.com\",\"c@example.com\"]}}",
"numberOfResults": 500,
"startRow": 0
}
}
Swap email for username if that’s what you have.
If your list is large, chunk it (e.g., 200–500 logins per request) and paginate with startRow / numberOfResults.
(Optional) Filter by last-login date with a range query on lastLoginInstant:
{
"search": {
"query": "{\"range\":{\"lastLoginInstant\":{\"gte\":\"2025-10-01T00:00:00Z\"}}}"
}
}
You can also query by epoch millis if you prefer.
Map results
Each user object includes
lastLoginInstant (epoch millis). Convert to your desired timezone/format in your script and write out a CSV.
Tips
If you need all users in a tenant (not just your list), you can search with a wildcard or a match-all query and page through results, then filter locally.
For ongoing metrics, consider subscribing to
user.login.success webhooks and recording last logins as they happen.
Docs:
Search for Users API (Elasticsearch):
https://fusionauth.io/docs/apis/users#elasticsearch-search-engine
