Applying a Template to a Product
Merge your design graphic onto every color variant mockup by combining a saved template with a new design graphic - then let PrntFlow upload and assign everything automatically.
Overview
Once you've created a mockup template, applying it to a product is the core workflow for generating 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: Upload Product Mockups Workflow
Select a Product
Use the product search box to find and select any Shopify product in your store. For the best results, choose a product with color variants - PrntFlow will automatically generate a unique mockup for each color.
Tip: From the Manage Templates page, each template card has an "Upload Product Mockups" button that pre-selects that template for you, saving a step in your workflow.
Select a Template
Choose a saved 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 UI will prompt you to create one first before you can proceed with uploading mockups.
Upload Your Design Graphic(s)
Upload the design graphic you want to appear on your t-shirt mockups. PrntFlow uses a two-graphic system to handle different color groups:
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 mockup generation.
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.
Generate Mockups
Once you've selected a product, chosen a template, and uploaded your design graphic(s), click the "Generate 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 generated images to Shopify and assigns them to the correct variants.
Progress Indicators:
You'll see real-time progress as PrntFlow works:
- • Rendering mockups X/Y – merging your design onto base mockups for each color
- • Uploading mockups X/Y – sending generated 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 generating and uploading mockups:
New Images in Product Media
The generated 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 during generation. PrntFlow only generates 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 generate 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 generated mockup size before uploading. If it exceeds Shopify's 20 MB limit, the app automatically retries at reduced 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?
No. PrntFlow only adds new images and links them to variants. It does not delete any existing product media. When you generate mockups, the new images are uploaded to your Shopify product media gallery and assigned to the appropriate color variants. Your existing images remain in Shopify unless you manually delete them. Even if you uninstall PrntFlow, all mockup images it generated will stay in your Shopify store.
Can I regenerate 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 generates 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.