| stats count is going to be your friend – and it’ll be faster than trying to use dedup, too:
myusername response_status="401"
| stats count by website website_url user_name transaction_name user
| fields - count
And if you want to then merely have a count of websites inside that list, add this:
| stats count by website
from User warren – Stack Overflow https://stackoverflow.com/questions/69749324/splunk-table-print-number-of-rows-per-selected-field/69760659#69760659
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