> For the complete documentation index, see [llms.txt](https://help.connected.illumina.com/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://help.connected.illumina.com/infectious-disease/dragen-16s-plus/dragen-16s-plus/how-to-set-up-and-run-an-analysis/custom-database-fasta-file-format.md).

# Custom database FASTA file format

#### Custom database FASTA files: <a href="#custom-fasta" id="custom-fasta"></a>

A custom database FASTA file containing up to 500 million basepairs of reference sequence may be specified using the exact FASTA header format defined below. In the FASTA file, the SequenceID should not contain any spaces. All sequences must have seven canonical taxonomic rank prefixes specified: k\_\_;p\_\_;c\_\_;o\_\_;f\_\_;g\_\_;s\_\_. However these can all be left blank except for (k)ingdom and (s)pecies designations, which are required.

To upload a custom database FASTA file, go to the "Projects" tab and click on the folded paper icon (representing File) to reveal a dropdown menu. Click on "Upload" and select "Files". Within the upload page, select "Other" format for FASTA files, and upload the file as a Biosample. Within the DRAGEN 16S Plus app, under "Custom database specification" use the "Custom reference for taxonomic classification" control to select the uploaded FASTA file.

#### Example custom database FASTA header format: <a href="#example-fasta" id="example-fasta"></a>

```
>SequenceID_001:k__Fungi;p__Glomeromycota;c__Glomeromycetes;o__Glomerales;f__Glomeraceae;g__;s__uncultured_Glomus
```


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