Marketplace · Creator Guide

Mockup Marketplace
Template Creator Guide

Everything you need to build, price, and submit canvas templates to the Kontraktr™ Marketplace — from specs to Stripe payout setup.

10 min read·Updated March 2026·Browse Marketplace

Canvas size requirements

Hard limits the editor enforces.

Width	600 px	Fixed — do not change
Height	600 px	Fixed — do not change
Background	"transparent"	Must be exactly the string "transparent"
Fabric.js version	6.0.0	Use the version string exactly as shown
Safe print area	480 × 480 px	Keep all key art within this centred zone (60 px padding)
Canvas centre	left: 300, top: 300	Use originX/Y: "center" for predictable placement

Design at 1× (600 px = 600 px). The editor scales down to fit smaller screens automatically — your layout won't be distorted.

Never set a solid background fill. Buyers layer your template on top of a garment photo. A solid background will hide the shirt.

JSON schema

The exact structure Kontraktr™ expects.

A canvas template is a single JSON object. Here is the minimum valid structure — one editable text layer on a transparent background:

json

{
  "version": "6.0.0",
  "background": "transparent",
  "objects": [
    {
      "type": "Textbox",
      "text": "YOUR TEAM NAME",
      "left": 300,
      "top": 220,
      "width": 400,
      "fontSize": 52,
      "fontFamily": "Impact",
      "fill": "#ffffff",
      "textAlign": "center",
      "originX": "center",
      "originY": "center",
      "selectable": true,
      "editable": true,
      "data": { "placeholder": "Team Name" }
    }
  ]
}

And here is a more complete two-layer example (a decorative circle that buyers can't move, plus two editable text fields):

json

{
  "version": "6.0.0",
  "background": "transparent",
  "objects": [
    {
      "type": "Circle",
      "left": 300,
      "top": 300,
      "radius": 180,
      "fill": "transparent",
      "stroke": "#ffffff",
      "strokeWidth": 4,
      "originX": "center",
      "originY": "center",
      "selectable": false,
      "evented": false,
      "lockMovementX": true,
      "lockMovementY": true
    },
    {
      "type": "Textbox",
      "text": "YOUR TEAM NAME",
      "left": 300,
      "top": 220,
      "width": 380,
      "fontSize": 48,
      "fontFamily": "Impact",
      "fill": "#FFD700",
      "textAlign": "center",
      "charSpacing": 80,
      "originX": "center",
      "originY": "center",
      "selectable": true,
      "editable": true,
      "data": { "placeholder": "Team Name" }
    },
    {
      "type": "Textbox",
      "text": "EST. 2024",
      "left": 300,
      "top": 370,
      "width": 200,
      "fontSize": 20,
      "fontFamily": "Arial",
      "fill": "#ffffff",
      "textAlign": "center",
      "charSpacing": 300,
      "originX": "center",
      "originY": "center",
      "selectable": true,
      "editable": true,
      "data": { "placeholder": "Established Year" }
    }
  ]
}

Validate your JSON at jsonlint.com before submitting. Malformed JSON will fail silently in the editor.

Supported object types

Every type the Mockup Editor can render.

Textbox

Multi-line editable text. Use for all buyer-editable copy.

Rect

Rectangle/square. Supports fill, stroke, and border-radius (rx/ry).

Circle

Perfect circle. Use radius to set size.

Line

Straight line from (x1, y1) to (x2, y2).

Triangle

Isoceles triangle. Use width and height to size it.

Path

SVG path data. Use for custom vector shapes.

Image

Raster image via URL. Must be publicly accessible.

Group

Group of objects that move and scale together.

Lock decorative elements by setting selectable: false, evented: false, lockMovementX: true, lockMovementY: true. Buyers can't accidentally drag them out of place.

Editable placeholders

How to mark text zones buyers should customise.

Add a data object to any Textbox you want buyers to edit. The Marketplace panel highlights these fields and prompts buyers to fill them in before printing.

json

{
  "type": "Textbox",
  "text": "YOUR CITY, ST",
  "left": 300,
  "top": 340,
  "width": 300,
  "fontSize": 22,
  "fontFamily": "Arial",
  "fill": "#cccccc",
  "textAlign": "center",
  "originX": "center",
  "originY": "center",
  "selectable": true,
  "editable": true,
  "data": {
    "placeholder": "City & State",
    "hint": "e.g. Austin, TX"
  }
}

data.placeholderrequiredShort label shown to the buyer. e.g. "Team Name", "City & State", "Year".

data.hintoptionalOptional example text shown below the field. e.g. "e.g. Austin, TX".

Use ALL-CAPS default text (e.g. "YOUR TEAM NAME") so it's obvious to buyers that this zone is a placeholder, not final copy.

Categories & tags

Help buyers find your template in search.

Pick the single most relevant category. Use 5–10 specific tags.

🎨Screen Print Separations

🖨️DTF-Ready Designs

👕Mockup Templates

✏️Fonts & Typography

📐Vectors & Clip Art

🧵Embroidery Files

🌈Sublimation Designs

📋Business Templates

📦Bundles & Collections

Good tag examples

varsitydistressedbaseballvintageyouth-sportsminimalretroboldcircle-badgetwo-color

Avoid generic tags like "design", "template", or "printable" — they don't help buyers find your work in search.

Pricing your template

Whole US dollar amounts. You keep 80%.

Free

Builds reputation fast. Gets priority placement in search. Great for your first 3–5 listings.

Single Template

$3–$15

Best range for individual mockup templates and artwork packs.

Bundle

$20–$50

5+ templates or full garment mockup sets. Buyers expect significant savings vs. individual pricing.

You earn 80% of every sale. Kontraktr™ takes a 20% platform fee and handles all payment processing, delivery, and refunds automatically. No subscription required to sell.

Setting up Stripe for payouts

Required before your first sale pays out.

Earnings accumulate in your seller balance. To withdraw, you need a connected Stripe account with identity verification and a bank account on file. This is a legal requirement — Kontraktr™ cannot bypass it.

1Go to Marketplace → My Seller Dashboard
2Click the "Payouts" tab
3Click "Connect Stripe Account"
4Complete Stripe's identity verification (5–10 minutes — have your SSN or EIN and a government ID ready)
5Add your bank account for ACH direct deposit
6Payouts run on the 1st and 15th of each month for any balance over $10

Payouts are only released after the buyer's 30-day refund window closes. Refunds are deducted from your next payout, not charged back to your bank account.

Connect Stripe before you publish your first listing — there is no waiting period once your account is verified.

Submitting your template

Step-by-step from editor to live listing.

1
Build in the Mockup Editor
Open any job and click the mockup editor, or go to Marketplace → "Create Template". Use the canvas tools to build your design.
2
Export the canvas JSON
Click File → Export → "Save as Marketplace Template". This copies the Fabric.js JSON to your clipboard.
3
Fill in the listing form
Name, description, category, tags, garment type, print location, and price. Description should mention the print method (screen print, DTG, heat transfer) the template is optimised for.
4
Upload preview images
Minimum 800×800 px PNG or JPEG. At least one image should show the template on a dark garment and one on a light garment. More images = more sales.
5
Submit for review
Click "Submit for Review". The Kontraktr™ team checks all listings within 2 business days. You'll receive an email when it's approved or if changes are needed.

Preview image requirements

What reviewers look for.

Minimum 800×800 px
PNG or JPEG
Show on both dark and light garments
Flat-lay or on-model photography
Clean, uncluttered background
3+ images preferred

Don't

Add "SAMPLE" text or watermarks
Blur or obscure the design
Use tiny thumbnails (<400 px)
Show competing brand logos
Use heavy Photoshop filters
Screenshot the editor UI

Review process & content rules

What gets approved and what gets rejected.

Every submission is reviewed within 1–2 business days. If your listing is rejected, you'll receive an email explaining why — fix the issue and resubmit with no limit on attempts.

Automatic rejection reasons

Copyrighted characters, logos, or trademarks (Disney, NFL, Nike, etc.)

Offensive, hateful, or discriminatory imagery or text

Canvas JSON that fails to load in the Mockup Editor

Incorrect Fabric.js version (must be 6.0.0)

Solid background fill (must be transparent)

No editable placeholder on templates that clearly need one

Preview images with watermarks, blurring, or competing branding

Misleading category (e.g. listing a Rect template as a Screen Print Separation)

When in doubt, email marketplace@kontraktr.io before submitting. The review team can pre-screen your template and give feedback.

Ready to publish your first template?

Apply as a seller, build in the Mockup Editor, and start earning on every download. Free to list.

Browse Marketplace Seller Portal Guide

Seller Portal

Manage listings, track earnings, withdraw via Stripe.

Browsing the Marketplace

Find and purchase templates as a buyer.

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{ "version": "6.0.0", "background": "transparent", "objects": [ { "type": "Textbox", "text": "YOUR TEAM NAME", "left": 300, "top": 220, "width": 400, "fontSize": 52, "fontFamily": "Impact", "fill": "#ffffff", "textAlign": "center", "originX": "center", "originY": "center", "selectable": true, "editable": true, "data": { "placeholder": "Team Name" } } ] }

{ "version": "6.0.0", "background": "transparent", "objects": [ { "type": "Circle", "left": 300, "top": 300, "radius": 180, "fill": "transparent", "stroke": "#ffffff", "strokeWidth": 4, "originX": "center", "originY": "center", "selectable": false, "evented": false, "lockMovementX": true, "lockMovementY": true }, { "type": "Textbox", "text": "YOUR TEAM NAME", "left": 300, "top": 220, "width": 380, "fontSize": 48, "fontFamily": "Impact", "fill": "#FFD700", "textAlign": "center", "charSpacing": 80, "originX": "center", "originY": "center", "selectable": true, "editable": true, "data": { "placeholder": "Team Name" } }, { "type": "Textbox", "text": "EST. 2024", "left": 300, "top": 370, "width": 200, "fontSize": 20, "fontFamily": "Arial", "fill": "#ffffff", "textAlign": "center", "charSpacing": 300, "originX": "center", "originY": "center", "selectable": true, "editable": true, "data": { "placeholder": "Established Year" } } ] }

{ "type": "Textbox", "text": "YOUR CITY, ST", "left": 300, "top": 340, "width": 300, "fontSize": 22, "fontFamily": "Arial", "fill": "#cccccc", "textAlign": "center", "originX": "center", "originY": "center", "selectable": true, "editable": true, "data": { "placeholder": "City & State", "hint": "e.g. Austin, TX" } }

Mockup Marketplace Template Creator Guide

Canvas size requirements

JSON schema

Supported object types

Editable placeholders

Categories & tags

Pricing your template

Setting up Stripe for payouts

Submitting your template

Preview image requirements

Review process & content rules

Ready to publish your first template?

Mockup Marketplace Template Creator Guide

Canvas size requirements

JSON schema

Supported object types

Editable placeholders

Categories & tags

Pricing your template

Setting up Stripe for payouts

Submitting your template

Preview image requirements

Review process & content rules

Ready to publish your first template?

Mockup Marketplace
Template Creator Guide

Mockup Marketplace
Template Creator Guide