Applying a Template to a Product
Select your product, your graphic for that product, and your PrntFlow template. PrntFlow applies the graphic to your t-shirt for each variant color you offer, then uploads and assigns these new mockup images to your product, all within the PrntFlow app within Shopify.
This short video shows how to apply a template to a product: pick the product and template, add your design graphic, and PrntFlow merges and uploads a mockup for every color.
Overview
Once you've created a mockup template, applying it to a product is the core workflow for merging variant-specific mockups. You combine a saved template (which defines colors, base mockups, and placement) with a new design graphic to produce merged mockup images for each color variant.
This process happens entirely within PrntFlow and results in new images being uploaded to your Shopify product media and assigned to the correct variants automatically.
Step-by-Step: Apply Mockups Workflow
Select a Product
Use the product search box to find and select any Shopify product in your store.
Tip: From the Manage Templates page, each template card has an "Apply to products" button that pre-selects that template for you, saving a step in your workflow.
Select a Template
Choose a saved PrntFlow template from the dropdown menu. The template defines which colors are available, which base mockup image belongs to each color, light/dark shirt groupings (if configured), and how your design should be placed and rendered.
If you've set a default template in Manage Templates, it will be pre-selected automatically to speed up your workflow.
Note: If you haven't created any templates yet, the app will guide you into creating your first template before you can proceed with applying mockups to any of your products. Template creating is super simple and a one time shot on a process you are already familiar with in your POD journey.
Upload Your Design Graphic(s)
Upload the design graphic you want to appear on this product's mockups. The PrntFlow template system offers a simple way to isolate your dark shirts from your light shirts, requiring in some cases a graphic for each: light and dark. Once set, you'll have two places to drop in the right graphic, one for dark shirts and a second for light shirts.
Default Design (Required)
This is the default graphic used for all colors, or specifically for dark-colored shirts if your template has light/dark color groupings configured.
You must upload at least one graphic to the Default Design to proceed with applying mockups.
Alternate Design (Optional)
If your template has light/dark color groupings configured, you can upload a different graphic as the Alternate Design for light-colored shirts, optionally. This is useful when you need light text on dark shirts and dark text on light shirts.
If the Alternate Design is left empty, all colors will use the Default Design graphic regardless of grouping.
Supported formats: PNG only
Maximum file size: ~50 MB per graphic
Dimension warning: If your uploaded graphic's dimensions differ significantly from the placeholder image used when creating the template, PrntFlow will show a warning that placement might not be exact. You can still proceed, but you may want to adjust the template or resize your graphic for best results.
Apply Mockups
Once you've selected a product, chosen a template, and uploaded your design graphic(s), click the "Apply Mockups" button to start the process.
PrntFlow merges your design onto each color's base mockup using the placement and settings saved in the template, then uploads the merged images to Shopify and assigns them to the correct variants.
Progress Indicators:
You'll see real-time progress as PrntFlow works:
- • Rendering mockups - merging your design onto base mockups for each color
- • Uploading mockups - sending merged images to Shopify's Product Media API
- • Success banner - Confirmation message when all mockups are uploaded and assigned
On success, a "View Product" button will appear, linking directly to the Shopify product page in your admin so you can review the newly uploaded mockups and variant assignments immediately.
What You'll See in Shopify
After PrntFlow finishes applying and uploading mockups:
New Images in Product Media
The merged mockup images appear in the product's media gallery in your Shopify admin, just like any other product image.
Variants Associated with the Right Mockup
Each color variant is automatically associated with its corresponding mockup image. When a customer selects a color on your product page, they'll see the correct mockup for that color.
Troubleshooting & Edge Cases
What if the template has colors the product doesn't?
Those extra colors are simply skipped. PrntFlow only merges mockups for colors that exist in both the template and the selected product. For example, if your template includes Black, White, Red, and Yam, but the product only has Black and White, PrntFlow will merge mockups for Black and White only.
What if the product has colors the template doesn't cover?
Those product variants won't receive new mockups in this upload and will keep their existing media. To add mockup coverage for additional colors, simply create a new template that includes them - it only takes a few minutes and the new template can be reused across all your products.
What if Shopify rejects an image for being over 20 MB?
PrntFlow checks the merged mockup size before uploading. If it exceeds Shopify's 20 MB limit, what happens next depends on your output format. With JPG output, the app automatically retries at reduced quality. With PNG output, the app first asks you, then re-exports the image as a JPG at 80% quality. If the image is still too large, you'll see an error - the most common cause is very high output dimensions set in Template Settings. Reducing your output width and height will resolve this.
Are existing product images deleted?
Yes. But the delete occurs at the end of the PrntFlow mockup assignment loop. Your new mockups appear instantly to shoppers on live products. And older images, most likely with multiple awkwardly positioned shots, like showing the back of the t-shirt which displays the graphic on the front, those images are deleted. No more unwanted images crowding your product page.
Those original images are not lost. Your print provider always retains the original mockups. For any reason should you want to bring back the original images, go to your print provider's app, find the product, select mockups and publish. The print provider mockups will then overwrite the PrntFlow delivered mockups.
Can I re-apply mockups if I change my design?
Yes. You can apply the same template to the same product as many times as you want with different design graphics. Each time, PrntFlow merges new mockup images, uploads them, and assigns them to the correct variants. Previous mockup images for that product are replaced automatically - your product media stays clean.