> For the complete documentation index, see [llms.txt](https://knowledge.illumina.com/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://knowledge.illumina.com/instrumentation/nextseq-500-550/instrumentation-nextseq-500-550-troubleshooting-list/000002067.md).

# Optimal cluster density guidelines for the NextSeq 500/550

The recommended raw cluster density for NextSeq 500/550 High-Output and Mid-Output runs is 170-220k/mm2 for well-balanced, base diverse libraries (eg, whole genome libraries, RNA-seq libraries, etc.).

For further information, search for Knowledge Base articles:

* **Cluster density guidelines for Illumina sequencing platforms.**
* **How to achieve more consistent cluster density on Illumina Sequencing Platforms.**

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| *For any feedback or questions regarding this article (Illumina Knowledge Article #2067), contact Illumina Technical Support* [*techsupport@illumina.com*](mailto:techsupport@illumina.com?subject=Question%2FFeedback%20Regarding%20Illumina%20Knowledge%20Article%20#000002067%20-%20Instrumentation%20\&body=Dear%20Illumina%20Technical%20Support,%0D%0A%0D%0A)*.* |


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