> ## Documentation Index
> Fetch the complete documentation index at: https://docs.xsdr.app/llms.txt
> Use this file to discover all available pages before exploring further.

# Firehose

Firehose, built by [Ahrefs](https://ahrefs.com/), is a persistent web crawler built for tracking mentions and changes at scale.

## Latency

The Firehose crawler needs to visit a web page in order to detect changes. It operates on it's own schedule. Generally, popular web pages are indexed faster than others.

Because of this, changes will not necessarily be delivered to XSDR in "real-time". They will be delivered as soon as the crawler detects a change.

## Rule Syntax

When building rules, Firehose supports [lucene queries](https://lucene.apache.org/core/2_9_4/queryparsersyntax.html). Refer to Firehose's [documentation](https://docs.firehose.com/stream/rules) for a full list of supported syntax.