> ## Documentation index
> Fetch the complete documentation index at: https://upstash.com/docs/llms.txt
> Ask it with GET https://upstash.com/docs/ask?q=<keywords or question>. Short keywords rank best.
> Use these to discover all available pages before exploring further.
> Feature requests: https://upstash.com/docs/common/help/feature-requests.md lists what users asked for and how to vote for a request or add one.
> Page rating: `GET https://upstash.com/docs/feedback?path=/docs/redis/commands/hyperloglog/overview&helpful=true` (or `false`) records whether this page helped. An optional `comment` (URL-encoded, at most 500 characters) says what was missing or wrong. It is anonymous and needs no key. Comments hold no code, secrets or personal data.

# HyperLogLog commands

> Commands for probabilistic cardinality estimation.

<CardGroup cols={2}>
<Card title="PFADD" href="/redis/commands/hyperloglog/pfadd">Add elements to HyperLogLog</Card>
<Card title="PFCOUNT" href="/redis/commands/hyperloglog/pfcount">Get estimated cardinality</Card>
<Card title="PFMERGE" href="/redis/commands/hyperloglog/pfmerge">Merge multiple HyperLogLogs</Card>
</CardGroup>