# Creating a custom genome for NovaSeq X Series
To use a custom reference genome with DRAGEN workflows on the NovaSeq X instrument, use the [BaseSpace Reference Builder (Instruments)](https://basespace.illumina.com/apps/17121104/Reference%20Builder%20%28Instruments%29%20) app to convert a reference genome in FASTA format to a hash table.
* Prior to selecting the "Launch Application" button, confirm which DRAGEN workflow version is on the instrument to ensure the appropriate hash table version of the reference is created by the Reference Builder (Instruments) app on Basespace. For example, version 4.3 workflows DRAGEN workflows require a v10 hash table reference. To ensure the correct selection of the app version, navigate to the app description section labeled **New Features** and check listed reference version:
* Select "Launch Application"
* Proceed with Application Configuration steps ensuring the **Instrument** series option **NovaSeq X Series** is selected
* Proceed with completing all subsequent steps
* Select **Launch Application**
* Once analysis completes a **v10.tar.gz** file is created that contains the reference genome. Download the reference genome.
* Add the reference genome file to the instrument by following the instructions outlined in the [user guide](https://support-docs.illumina.com/IN/NovaSeqX/Content/IN/NovaSeqX/ImportResources.htm).
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