You can import or bulk-update Custom Attributes on your Product Catalog items using a CSV file, the same way you'd import Item Specifics for eBay listings. This lets you add brand-specific details (Material, Type, Color, etc.) to hundreds of products at once, or update existing values in bulk.
What are Custom Attributes?
Custom Attributes are the flexible, extra fields on a Catalog product that sit alongside the built-in Product Properties (Title, SKU, Price, etc). They're either created automatically when you import listings from a channel, or created manually to store your own data (Material, Warranty, Supplier Cost, and so on).
👉 For a full explanation of Product Properties vs Custom Attributes and how they're used in mapping and rules, see: Understanding Product Properties & Custom Attributes in the 3Dsellers Catalog.
The CSV Format: Use "C: " Before the Attribute Name
To import or update a Custom Attribute, add a column with "C: " followed by the exact attribute name.
This works the same way as importing eBay Item Specifics with the "C:" prefix - it's the same convention, just applied to your Product Catalog.
SKU | C: Type | C: Material |
SKU001 | Bicycle Chainring | Chrome |
SKU002 | Bike Pedal | Aluminum |
SKU003 | Saddle | Leather |
Each "C: " column becomes its own Custom Attribute on the product. You can add as many "C: " columns as you need - one per attribute.
Notes:
The attribute name after "C: " must match the Custom Attribute name exactly if you're updating an existing attribute. If no attribute with that name exists yet, 3Dsellers will create one automatically.
Don't use "C: " for fields that already exist as a standard Product Property (SKU, Title, Price, Brand, Condition, etc). Use the regular column name for those instead - "C: " is only for Custom Attributes / Item Specifics data.
Column name matching is not case-sensitive, but keep your naming consistent across rows and future imports to avoid creating duplicate attributes with slightly different names (e.g. "Material" vs "material").
Custom attribute, same as item specifics don't need to be mapped in the CSV mapping.
How to Import
Prepare your CSV with a SKU column (required to match products) plus one "C: " column per Custom Attribute you want to set.
Go to Products in the Product Catalog.
Click Import (top-right) and choose Create New Products from CSV if you're adding new products, or use Update Products from the Import/Export Files page if you're updating existing ones.
Upload your file and go through the mapping screen as usual for your standard fields. Your "C: " columns don't need manual mapping - they're picked up automatically as Custom Attributes.
Start the import and check the Import/Export Files page for status and any row-level errors.
💡 For the full step-by-step on uploading, mapping, and running catalog imports, see: Creating New Products with CSV Files in 3Dsellers and How to Bulk Update Products Catalog with a CSV File.
Using Separate Name/Value Columns (Alternative Format)
If your source data already has attribute names and values in separate columns (common when exporting from other software), you can use this format instead:
SKU | Attribute1Name | Attribute1Value | Attribute2Name | Attribute2Value |
SKU001 | Type | Bicycle Chainring | Material | Chrome |
SKU002 | Type | Bike Pedal | Material | Aluminum |
Increase the number (Attribute1, Attribute2, Attribute3...) for each additional attribute pair you need to include.
Verifying Your Import
After the import finishes, open a few products and check the Custom Attributes section (in the product editor, or under General Details) to confirm the new values landed correctly. Any new attribute names from your CSV will now also be available to map in your Channel Template Mapping.
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