Mockup Image Guide: Size, Shape, Background and Format

What size should your t-shirt mockups be, what shape, and what file type? This guide explains how PrntFlow uses your mockups, what we recommend, and what Shopify, Meta and Google expect from your product photos.

The quick answer

Why your mockup images matter

On a t-shirt store, the product photo does most of the selling. Shoppers buying on impulse decide in a second or two, usually on a phone, often from an ad. A soft, stretched or badly framed photo makes a good design look cheap.

PrntFlow turns your mockups into those product photos. It merges your design onto each color's mockup and uploads the finished images to Shopify. Shopify shows them on your product and collection pages, and your sales channels send them to Facebook, Instagram and Google Shopping for your ads. So the mockup you upload into a PrntFlow template ends up everywhere your product is sold. Get it right once and every one of those places benefits.

How PrntFlow uses your mockup

Each template has an output size: the pixel size of the finished images. The default is 2048 × 2048 px. You can change it for your whole store in Settings, or per template in Template Settings. The largest output size is 4000 × 4000 px.

When PrntFlow builds a finished image, it resizes your mockup to exactly the output size. Three things can happen:

Size warnings

PrntFlow warns you on the Upload Mockups and Edit Mockups pages and in Template Settings when a mockup:

• will be enlarged by more than 1.25x
• will be stretched (its shape is more than 2% off the output size)
• is under 800 px on its shortest side

Warnings never block you. If a template is set up that way on purpose, untick "Warn me when mockup sizes don't match the output size" in its Template Settings. The box is ticked by default.

Our defaults and recommendations

Why 2048 × 2048?

Square 2048 × 2048 px is our recommended size and our default, and the size Shopify recommends for square product images: "for square product images, a size of 2048 x 2048 px usually displays best." If you choose a different output size, anything from 1500 to 2500 px on the longest side works well. 2048 is big enough for zoom and sharp on high-resolution phone and laptop screens. Shopify accepts product images up to 5000 × 5000 px and under 20 MB, so 2048 leaves plenty of room. Your theme asks Shopify for smaller copies sized for each screen, so a 2048 px original doesn't slow your pages down.

Why JPG?

At 80 to 85% quality, a JPG looks the same as the original to the eye at a fraction of the file size. Shopify's image service already converts your images to modern formats like WebP for shoppers' browsers, so you lose nothing by uploading JPG. JPG is also accepted everywhere your images travel, including Meta's catalog.

Square or not?

Square is the safe choice.

Collection pages and product grids

Product grids line up best when every image has the same shape. Many themes, including Shopify's Dawn, show product cards at each image's own shape by default ("Adapt to image"), so mixed shapes give you an uneven grid. Themes that crop cards to a fixed shape (Dawn offers Square and Portrait) cut the edges off anything that doesn't match. A square image looks right either way.

Product pages

Whatever shape PrntFlow outputs is the shape the shopper sees. A stretched image shows up as it is, stretch and all.

Ads

Meta asks you to keep every image in a catalog at the same aspect ratio, either 1:1 square or 4:5. If they're mixed, carousel ads may auto-adjust them. A square template gives you one shape for every color automatically.

If you do choose another shape, choose it for the whole template: set the output size to that shape, and upload every mockup at that same shape and size.

Resolution: how small is too small

Watch out for mockups saved from a website or a screenshot. They're often only 400 to 600 px, even when they look fine on your screen. Download the full-size file from your mockup source instead.

There's no pixel limit on uploads, only a 50 MB file size limit, so a large mockup is never a problem. PrntFlow scales it down cleanly.

Backgrounds

Transparent mockups work

Some mockups, such as many ghost mannequin mockups, come as PNG files with a transparent background around the shirt. PrntFlow fills every transparent area with your Background color: white (#ffffff) by default. Set it for your whole store in Settings, or per template in Template Settings.

Partly transparent areas, like soft shadows and the edges of the shirt, blend smoothly into that color. Mockups without transparency come out exactly as before. Every finished image has a solid background, never a transparent one.

Which color?

White and light neutral backgrounds are the most common. The best choice is usually the background color of your own product pages, so the photos blend in. Remember the same image also shows on collection pages, your home page and in ads.

File formats

Why design graphics must be transparent PNGs

PrntFlow merges your design onto the shirt, so everything around the artwork has to be transparent for the shirt to show through. JPG can't store transparency, so it isn't accepted. The PNG you send your print provider usually works as it is.

Why there's no WebP output

Meta's catalog accepts JPEG and PNG only, and Shopify already creates WebP copies for shoppers' browsers from your original. A WebP upload would gain nothing on your store and could break your Facebook and Instagram catalog.

If a finished image is over 20 MB

Shopify rejects images of 20 MB or more. With JPG output, PrntFlow retries at lower quality automatically. With PNG output, PrntFlow asks you first, then re-exports the image as a JPG at 80% quality.

Facebook and Instagram (Meta)

If your store uses the Facebook & Instagram sales channel, Shopify syncs your products to your Meta catalog. For a product with variants, Meta usually syncs one image per variant: the image set on that variant in Shopify, or the product's main image if the variant has none. PrntFlow sets each color's mockup as that color's variant image, so each color's mockup is the image Meta uses for that color. The product's main image in the catalog is its first, largest image in Shopify.

Meta uses these images in Advantage+ catalog ads (formerly dynamic product ads). Each ad shows one variant of a product, and Meta says its ad delivery system "automatically shows the most relevant variant to each person." When someone taps through, they can see the other variants. So any color's mockup can be the one a shopper sees first, which is why every color needs its own sharp, consistent mockup.

A 2048 × 2048 px image is well above the Shops sizes. Shopify sends resized copies to its sales channels rather than your original file, so PrntFlow's finished images fit well inside the 8 MB limit.

What Meta recommends

Meta's own image tips line up with PrntFlow's defaults:

• "Use product images with a white backdrop." PrntFlow's default background color is white.
• "Provide images in JPEG format over PNG where possible for best image quality." PrntFlow's default output is JPG.
• Keep every image in the same aspect ratio. PrntFlow outputs the same size for every color in a template.
• No text over the product, and no calls to action, promo codes or watermarks.

Cropping

In Commerce Manager, go to Catalog > Settings to choose how Meta crops your images: Fill frame (the default), Show entire image, or Crop and resize, which Meta says "works best with white or transparent backgrounds". Leave some room around the shirt so a crop doesn't cut into it.

Updating images

Meta only refreshes a replaced image when it has a new URL. Every time you apply mockups with PrntFlow, it uploads new images to Shopify, so re-applied mockups always get new URLs. Changes can take up to a day to show in your ads.

If you want a border or label on your catalog ads, use Meta's image templates rather than adding it to the mockup. Image templates replace catalog ad frames, which stop working after October 30, 2026.

Google Shopping and Merchant Center

If your store uses the Google & YouTube sales channel, Shopify sends your products and images to Google Merchant Center. Google uses them in Shopping results, the Shopping tab and Shopping ads.

Staged or lifestyle images that clearly show the product are also fine.

What Google doesn't allow on the main product image

Google's image rules ban overlays and extras on the main image, including:

• Watermarks
• Promotional text such as "best" or "cheap", prices, "free shipping" and calls to action like "buy"
• Your store name or logo, unless it's printed on the product itself
• Borders around the image

A clean mockup with no text added is safe. Your design printed on the shirt is part of the product, so it's fine.

Quick checklist

• Output size is 2048 × 2048 px, or one size you chose on purpose
• Every mockup is uploaded at exactly that size
• Every color's mockup has the same framing
• If your mockups have transparent areas, the Background color matches your store
• Output format is JPG at 80 to 85%
• Design graphics are transparent PNGs
• No added text, badges or borders on the mockup
• No PrntFlow size warnings on Upload Mockups, Edit Mockups or Template Settings

New to templates? Start with Mockup Templates: How They Work. For design graphic and print file sizes, see the T-Shirt Print Area Guide.

Sources

• Shopify Help Center, Product media types: 2048 × 2048 px recommendation, 5000 × 5000 px maximum, 20 MB file limit
• Shopify developer docs, image_url filter: themes request resized copies; Shopify serves WebP or AVIF automatically
• Meta, catalog fields reference: JPEG or PNG, at least 500 × 500 px, up to 8 MB
• Meta, product image specifications for catalogs: JPEG or PNG up to 8 MB, Shops sizes, white backdrop, JPEG over PNG, one aspect ratio, crop settings, new URL for replaced images
• Meta, how product images from Shopify are synced: one image per variant, main image
• Meta, about variants in your catalog: one variant per ad, the most relevant variant for each person
• Meta, frames in Advantage+ catalog ads: frames replaced by image templates, ending October 30, 2026
• Google Merchant Center, image requirements: formats, sizes, backgrounds, and banned overlays
• PrntFlow app behavior and guidance (resizing, warnings, defaults, formats, the 1500 to 2500 px output range), September 2026