> 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/iseq-100/instrumentation-iseq-100-faq-list/000006506.md).

# How to determine whether custom primers were selected on the iSeq 100 once the run is completed?

To determine whether custom sequencing primers were selected for an iSeq 100 run, check the "\<Planned\_Custom\_Primer>" line in the RunParameters.xml that contains a line for each of the reads indicating **if** custom primers were selected.

The RunParameters.xml file can be found in either the designated output location or the iSeq 100 Temp folder (D:\Illumina\iSeq Runs\[Runfolder]).

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| *For any feedback or questions regarding this article (Illumina Knowledge Article #6506), contact Illumina Technical Support* [*techsupport@illumina.com*](mailto:techsupport@illumina.com?subject=Question%2FFeedback%20Regarding%20Illumina%20Knowledge%20Article%20#000006506%20-%20Instrumentation%20\&body=Dear%20Illumina%20Technical%20Support,%0D%0A%0D%0A)*.* |


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