CSV Product Import to Shopify

I have a single CSV that contains all of my store’s products, and every item comes with its own set of variations (sizes, colors, etc.). I need the whole catalog migrated cleanly into my Shopify store so that each product displays its variants exactly as defined in the file.

The CSV may also include a few custom columns—at this point I’m not completely sure—so I’ll need you to flag any non-standard fields and advise on the best way to map or create them inside Shopify without breaking the import.

Deliverables:
• All products and their variants uploaded and visible in Shopify.
• Any custom fields clearly mapped or, if impossible, a brief note explaining why.
• A short hand-off summary outlining the steps taken, so I can repeat the process later if needed.

Please be comfortable working with Shopify’s bulk import tools and CSV editors. Accuracy is more important to me than speed; I want the storefront to go live with zero missing variants or broken links.