## Available formats
The Optimizely Recommendations engine can process product feeds in the following formats. The most commonly used is the XML in RSS 2.0 format.
**RSS format** – Really Simple Syndication, a dialect of XML.
This is the preferred format for Optimizely Recommendations.
An RSS feed is a standardized XML format that can be easily viewed and managed using an RSS reader. You can import product data in a quick, automated fashion.
Optimizely Recommendations supports XML feed formats in RSS 2.0 format. When you upload a feed to an Optimizely database, the application first checks to make sure that the RSS is valid.
**Custom XML feed** – Data wrapped in specific tags.
XML (Extendable Mark-up Language) lets you define your own elements for sharing stored structured data.
**Delimited**(Tab, CSV, and so on)
The file must be delimited. Tabs, commas, or pipes are preferred but the delimiter can be any character not present in the catalog data. If the delimiter has to be part of a value, it should be enclosed.
All values must be enclosed within a unique identifier.
For example, “X”,”Y”,”Z”, where Z contains a comma (,) as in the following example.
The first line of the file is the header. It must contain attribute names, separated by delimiters.
One item per line. Separate each attribute in each line by a delimiter.
All feeds must be UTF-8 compliant plain text.