About indexed field extraction
Splunk software can extract the following fields at index time:
- Default fields
- Custom fields
- File header fields
Splunk software always extracts a set of default fields for each event. You can configure it to extract custom fields and, for some data, file header fields.
When Splunk software indexes data, it parses the data stream into a series of events. As part of this process, it adds a number of fields to the event data. These fields include default fields that it adds automatically and any custom fields that you specify.
The process of adding fields to events is known as field extraction. There are two types of field extraction:
- Indexed field extraction, which was described briefly at the start of this topic and which forms the basis for this chapter. These fields are stored in the index and become part of the event data.
- Search-time field extraction, which takes place when you search through data. Splunk software creates those fields when compiling search results and does not store them in the index. See About fields in the Splunk Enterprise Knowledge Manager Manual for information about this type of field extraction.
There are two types of indexed fields:
- Default fields, which Splunk software automatically adds to each event. See About default fields in this chapter.
- Custom fields, which you specify. See Create custom fields at index time in this manual.
Note: When working with fields, consider that most machine data either does not have structure or has structure that changes constantly. For this type of data, use search-time field extraction for maximum flexibility. Search-time field extraction is easy to modify after you define it.
Tune timestamp recognition for better indexing performance
About default fields (host, source, sourcetype, and more)
This documentation applies to the following versions of Splunk Cloud™: 7.2.4, 7.2.6, 7.2.7, 7.2.8, 7.2.9