The blind download problem
When you sell an STL on Ko-fi, your buyer sees whatever images you manually uploaded — usually a render from your slicer or modeling software. They click buy, download the file, open it in PrusaSlicer or Chitubox, and only then discover if the mesh is watertight, if the proportions match, if the model needs supports.
This friction is unique to 3D files. A buyer of a PDF or font can see exactly what they get from a thumbnail. A buyer of an STL cannot — not without opening the file in specialized software.
Proofly embeds a full WebGL viewer on every listing. Buyers rotate the model, zoom in on details, and inspect topology before committing. Sellers with complex geometry (minis, mechanical parts, architectural models) see measurably higher conversion because buyers are more confident.
Ko-fi is free — but so is Proofly
Ko-fi's free tier charges a 5% platform fee on Shop sales (product downloads). Ko-fi Gold ($6/month) removes this fee — but adds an annual subscription cost. At $10/model × 100 sales, Gold breaks even at around year 1 before you're actually ahead.
Proofly also takes 0% from sellers — no subscription, no monthly fee, no tier system. The platform earns through a small flat fee paid by the buyer, not the creator. This applies to every sale, forever, from the first upload.
Revenue calculator
| Yearly (600 sales) | Ko-fi Gold | Proofly |
|---|---|---|
| Gross revenue | $7,200 | $7,200 |
| Platform cost (from seller) | −$72/yr Gold | $0 |
| Net to creator | $7,128 | $7,200 |
You keep an extra $72/yr on Proofly vs Ko-fi Gold
When someone leaks your file
STL files get pirated constantly. Discord servers, Telegram groups, and piracy forums redistribute premium STL packs within hours of purchase. Ko-fi offers no technical response to this — your only option is DMCA takedown requests, which are slow, manual, and reactive.
Proofly's HiddenMark system takes a different approach: every paid download is automatically fingerprinted with a unique steganographic code embedded inside the mesh geometry (not in metadata, which gets stripped by reslicers). Each code is unique to the buyer and purchase.
If a file surfaces on a piracy forum, upload it to proofly.store/hiddenmark and the system identifies exactly which buyer it came from. You go from «my file was pirated» to «buyer #1042 leaked it» in seconds.
🔐 HiddenMark™
Automatic per-buyer fingerprinting on every paid download. You don't set it up — it happens at the moment of purchase.
How HiddenMark works →Ko-fi is a general store. Proofly is a 3D marketplace.
Ko-fi is designed for creators broadly — illustrators selling art packs, musicians selling stems, writers selling PDFs. 3D model sellers on Ko-fi are one niche among many, and the platform reflects that: no format-specific search, no 3D viewer, no print settings fields, no topology analysis.
Proofly is built exclusively for 3D. Buyers browse by format (STL vs GLB vs 3MF), filter by category, and see a live 3D preview before purchasing. Sellers get an AI topology check before listing, print settings fields (material, layer height, support requirements), and HiddenMark protection on every sale.
The 3D-print audience is accustomed to tools like PrusaSlicer that show them exactly what they're working with. A blind-download storefront is a friction point they tolerate on Ko-fi because there's no better option — until now.
You don't have to choose
Proofly doesn't require exclusivity. If you have an existing Ko-fi shop with a loyal supporter base, keep it. Use Proofly to reach the 3D-print-specific audience that comes looking specifically for STL and GLB files, expects an in-browser preview, and is willing to pay more for models they can inspect before buying.
Uploading takes about 2 minutes. The 3D viewer is automatic — just upload your file and Proofly handles the rest. HiddenMark activates on every paid download with no extra steps.
Frequently asked questions
Can buyers preview 3D models before buying on Ko-fi?
No. Ko-fi shows only static images — buyers download STL files blind. Proofly includes a full in-browser 3D viewer (WebGL, no plugin) on every listing so buyers can inspect before purchasing.
Does Ko-fi protect 3D files from piracy?
Ko-fi has no piracy-tracing for 3D files. Proofly's HiddenMark embeds a unique fingerprint per buyer in every mesh. If your file leaks, upload it to proofly.store/hiddenmark to identify the source.
What percentage does Ko-fi take from 3D model sales?
Ko-fi's free tier charges 5% on Shop sales. Ko-fi Gold ($6/month) removes that fee, but adds an annual cost. Proofly takes 0% from sellers — no subscription, no tier system. The buyer pays a small flat fee instead of a percentage.
Can I sell on both Ko-fi and Proofly?
Yes. No exclusivity required. Cross-list freely to reach both your Ko-fi supporters and Proofly's 3D-print-focused buyer audience.
Is Proofly only for STL files?
No — Proofly supports STL, GLB, OBJ, 3MF, FBX, GLTF and ZIP packages. All 3D formats get a viewer and HiddenMark protection.
Built for 3D — not just digital files
Upload your first model in 2 minutes. In-browser viewer, HiddenMark protection, and 0% seller fees — no subscription required.
Start selling on Proofly →