Bulk Import Product Image Galleries from a Supplier CSV

Supplier files often spread product photos across several columns. See how Portaim turns image_1, image_2, image_3 into a real Shopify image gallery.

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The problem: many image columns, one gallery

Product photography rarely lives in one place in a supplier file. Wholesalers ship files with three to ten image columns per row — image_1 through image_8, or front_image, back_image, detail_1, detail_2. Some products have every column populated, some have only the front photo.

Shopify does not accept that shape. Its product CSV expects one image per row — each with the product’s Handle, one Image Src, and an Image Position. If you import a supplier row with multiple image columns as-is, Shopify only picks up whichever column you mapped to Image Src; every other photo is discarded.

The shape has to flip — from wide (many columns per row) to long (many rows per product):

Done by hand, this is the loop:

• duplicate each product row once per image column that has a value;
• on each duplicate, keep the Handle, clear the other product fields, and fill Image Src with the URL from one image column;
• set Image Position to 1, 2, 3 on each duplicate;
• check no row has a stale Title or Vendor that will overwrite the product on re-import;
• repeat next month.

How Portaim helps

Portaim recognizes URL-shaped columns during mapping and offers to expand them into a Shopify image gallery. Rather than picking one column and losing the rest, the expand rule turns each populated image URL into its own Shopify row — sharing the product’s Handle and carrying its own Image Position.

You keep control of:

• which supplier columns are grouped into the gallery (drop thumbnail if you do not want the low-res version at position 1);
• the column order — that order determines the Image Position in Shopify, so the first non-empty column becomes the primary image;
• detected-but-dropped columns are surfaced separately — if you remove an image column from the group, a “More image columns detected” chip lets you add it back with one click, so nothing gets silently missed.

Alt text is a separate mapping

Shopify’s Image Alt Text is one value per product — it lands on the product’s position-1 image row, which is the row Shopify actually shows in product listings and merchandising. It is not part of the image expand.

Two paths:

• If your supplier file has an alt-text column, map it directly to image_alt_text. The value copies straight to the product’s position-1 row.
• If it doesn’t, the mapping page shows a “fields we can generate with AI” hint — one click adds image_alt_text as an empty column. In the fix step, an “Enhance with AI” group asks the AI to write descriptive alt text per product from its title, description, and other context. Values are capped at 125 characters to keep them within accessibility best practice.

Sparse and inconsistent galleries

Real image columns are rarely uniform. Portaim handles the common trouble cases explicitly rather than silently:

Shopify’s CSV importer needs to reach each URL to fetch the photo, so publicly accessible https URLs are required. Portaim flags URLs that Shopify would reject before you hit export, not during Shopify’s side of the import.

Export — what the Shopify payload looks like

After mapping, a supplier row with three populated image columns becomes three Shopify rows — each sharing the same Handle, each carrying its own image URL and position:

Only the first row of each product carries the full product fields (Title, Vendor, Type, Image Alt Text, etc.). Subsequent rows leave those blank so Shopify treats them as gallery rows for the same product, not new products with the same handle. Direct Shopify export produces the same shape through the Admin API.

Portaim’s “Preview — what Shopify will receive” tab shows the same shape in the app before you export — row-type badges make the grouping obvious at a glance:

Repeat imports from the same supplier

A supplier’s image-column layout is one of the least fun parts of manual CSV work to redo every month. Portaim recognizes when the same layout is uploaded again and reapplies your expand rule — which columns are grouped and their order — along with your alt-text mapping (whether it was a supplier column or an empty column added for AI generation).

New products flow through with full galleries; discontinued products come out of the export set the same way any other row does; you spend your time on new merchandising decisions rather than re-teaching Portaim how the supplier ships photos.

When this fits

Portaim’s expand rule is a good fit if:

• your supplier file has multiple image columns per product row (three, five, eight);
• the columns hold public image URLs that Shopify will be able to fetch;
• you want a real Shopify image gallery, not just the front photo;
• the same supplier will send another file next month with a similar layout.

Portaim’s expand rule is not the right tool if:

• your supplier already ships images as one URL per row (each photo on its own line with a repeated Handle) — a straight Image Src mapping is enough;
• your image URLs are behind authentication or on a private network — Shopify cannot fetch them regardless of tooling;
• your supplier attaches images as separate binary files rather than URLs — those need to be uploaded to a public host (S3, R2, Cloudinary) before either Portaim or Shopify can use them.

Manual row duplication vs Portaim

The manual path is the loop from the top of this page. For a catalog with 500 products and up to eight images each, that is potentially 4,000 spreadsheet operations — every duplication a chance to accidentally overwrite a product field or miss a photo.

Portaim collapses it to a single mapping choice:

Supplier CSV/XLSX → Portaim mapping (group + expand + validate URLs) → Shopify-ready export

You group your image columns once, order them once, and let the expand rule handle every product row. Invalid URLs and http:// vs https:// issues surface in the fix step before export, not in Shopify’s import error log.

For the full mapping-and-validation flow around this step, see the supplier CSV to Shopify use case. For splitting a “Red / Large” variant column into real Shopify options, see the variant options guide.

Frequently asked questions