Final answer:
The Heavy Forwarder is the type of Splunk forwarder that can parse data before sending it to an indexer. It's more capable than a Universal or Light Forwarder, which focus on efficiently forwarding data with minimal or no parsing.
Step-by-step explanation:
The Splunk forwarder type that allows parsing of data before it is forwarded to an indexer is the Heavy Forwarder. Unlike the Universal Forwarder, which is designed for speed and efficiency in simply collecting and forwarding data without parsing, the Heavy Forwarder has the capability to parse and index the data if necessary, which involves processes such as event breaking, annotation with metadata, or routing of events to specific indexers.
A Light Forwarder would be an in-between choice with limited parsing capabilities, but it is worth noting that as of more recent Splunk versions, the Light Forwarder functionality has been deprecated. The Indexer actually does the heavy lifting of indexing the data and is not a forwarder at all.