Currently only the CSV file you get when exporting your collection from Rebrickable as a Rebrickable CSV file is supported.
- If you don't have one already, you'll need to create a Rebrickable account and then add your sets and parts to your collection.
- Once you've done that, you can export your collection as a Rebrickable CSV by selecting "My LEGO" → "All My Parts" from the main navigation, and then "Export Parts" → "Rebrickable CSV" from the left hand side of the page.
If you find that this information is not accurate, please do let me know so that I can update it to make things a little easier for others.
My CSV file keeps being rejected, what's going on?
You need to make sure you're using a Rebrickable Parts CSV – it should only contain Part, Color and Quantity columns. If you're certain that your CSV file is correctly formatted, please do let me know so that I can look into it for you.