# DRAGEN reference differences for on instrument and standalone analysis

DRAGEN uses references that are in a custom binary format, converted from FASTA files, generally. Depending on the platform on which analysis is occurring (DRAGEN server vs. Illumina instrument), the source of the DRAGEN reference is different, so it is important to use a reference specific to the location where the analysis will occur.

References built specifically for instruments contain an extra genome.json file that stores information such as genome name and hash table version. These fields in the genome.json file are used for error checking during run setup. For example, for an on-instrument DRAGEN workflow, when a reference is selected (by including it in the sample sheet), the pre-run check will check for consistency between the field in the sample sheet and the field in the genome.json file. If the reference listed in the sample sheet does not match the information in the genome.json file (or if the genome.json file is missing) users will encounter an error during pre-run check.

Illumina offers pre-built references for download either for on-premise DRAGEN server analysis or for on-instrument DRAGEN analysis for compatible instruments.

* For DRAGEN server analysis reference files can be found at [Illumina DRAGEN Bio-IT Platform Product Files](https://support.illumina.com/sequencing/sequencing_software/dragen-bio-it-platform/product_files.html)
* For NextSeq 1000/2000 instruments (running Control Software 1.7), reference files can be found at [DRAGEN Reference Genome Files for NextSeq 1000/2000 Control Software v1.7](https://support.illumina.com/downloads/dragen-compression-reference-genome-files-nextseq1000-2000-csw-1-7.html)
* For the NovaSeq X Series v1.3, reference files can be found at [DRAGEN Reference Genome Files for NovaSeq X Series v1.3](https://support.illumina.com/downloads/novaseq-x-v1-3-dragen-reference-genomes.html)
* For the MiSeq i100 Series, reference files can be found at [DRAGEN Reference Genome Files for MiSeq i100 Series](https://support.illumina.com/downloads/miseq-i100-series-dragen-reference-genomes.html)

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| *For any feedback or questions regarding this article (Illumina Knowledge Article #9589), contact Illumina Technical Support* [*techsupport@illumina.com*](mailto:techsupport@illumina.com?subject=Question%2FFeedback%20Regarding%20Illumina%20Knowledge%20Article%20#000009589%20-%20Software%20\&body=Dear%20Illumina%20Technical%20Support,%0D%0A%0D%0A)*.* |


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