> 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/microarray/general/microarray-general-troubleshooting-list/000001484.md).
# How to identify which Manifest and Cluster Files were used to generate a GTC File?
Illumina software such as Beeline, GenomeStudio, or BlueFuse Multi may return errors when loading a GTC (Genotype Call) file if the Product Files (Manifest and/or Cluster File) do not exactly match those used during GTC generation.
To ensure compatibility, follow the steps below to identify the Product Files used during GTC generation:
1. Right click the GTC file and open it in a text editor, like Notepad++.
**Figure 1.** Open a GTC file with a text editor.
2. The GTC file is encoded in a non‑human‑readable (binary) format, however, certain embedded text strings—such as the Manifest and Cluster file names—remain human‑readable.
3. Use the search function (Ctrl+F) in the text editor and search for “.bpm”, which is the file extension for the manifest file.
4. Similarly, use Ctrl+F to search for “.egt” to locate the cluster file name.
**Figure 2.** Identifying the product files (manifest and cluster files) used to generate a GTC file.
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| *For any feedback or questions regarding this article (Illumina Knowledge Article #1484), contact Illumina Technical Support* [*techsupport@illumina.com*](mailto:techsupport@illumina.com?subject=Question%2FFeedback%20Regarding%20Illumina%20Knowledge%20Article%20#000001484%20-%20Microarray%20\&body=Dear%20Illumina%20Technical%20Support,%0D%0A%0D%0A)*.* |
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