The problem: you can't prove ownership after the fact
If you sell 3D print files online, you've almost certainly thought about piracy. Maybe one of your best STL designs ended up on a free forum. Maybe a buyer resold your file without permission. Or maybe you're just wondering: if this happens, what can I actually do?
The hard truth is that most protection methods don't work. Watermarks on preview images get cropped. Metadata gets stripped when someone opens and re-exports your file. Password-protected ZIPs are trivially unlockable. Even "trusted buyer" systems give you no way to trace a leak after the fact.
The problem isn't piracy itself — it's that you can't prove ownership, trace a leak, or identify the buyer who shared it.
Visible vs. mesh watermarks: what actually survives
There are two categories of watermarking for 3D files:
Visible watermarks
A logo on the preview render, a text overlay on the thumbnail, or a branded base plate attached to the model. They signal ownership but are trivially removed — anyone can delete a base plate in Meshmixer in 30 seconds.
Mesh watermarks (steganographic)
Instead of adding visible content, they encode data directly into the geometry — into vertex positions themselves — at a level invisible to the eye and imperceptible in a print. The data survives format conversion (STL → OBJ → GLB), re-export, and even partial slicing. This is the approach HiddenMark uses.
How HiddenMark works
When a buyer purchases a model on Proofly, the platform automatically generates a unique watermarked version of the file before delivering the download. Here's the pipeline:
- Mesh analysis — the STL geometry is analyzed to find the thickest interior region using a signed-distance field (SDF) and distance transform on a voxelized volume.
- Code generation — a unique alphanumeric code (e.g. "HM·7F2A3B") is generated for this specific purchase and registered in the Proofly database.
- Embedding — the code is embedded as a tiny 3D text shape inside the mesh's inner volume and written into the STL binary header.
- Delivery — the uniquely marked file is delivered to the buyer; the original is never modified.
If a marked file surfaces on a piracy forum, anyone can upload it to proofly.store/hiddenmark and verify the embedded code in under one second.
Who benefits most from mesh watermarking
Miniature & figurine designers
Detailed sculpts are frequently uploaded to piracy aggregators — the watermark traces the exact buyer.
Engineering & functional parts
Proprietary tolerances and fitment data are costly to develop. Protect and trace leaks.
Architectural & terrain sets
Multi-file packs are often re-distributed on Discord. Each file in a pack is independently watermarked.
Character sculpts & cosplay props
High-resolution character files sold for resin printing are among the most-pirated 3D formats.
FAQ
Does the watermark affect print quality?
No. The embedded text is placed inside the mesh's inner volume — invisible in the final print and imperceptible after slicing. Prints look and function identically to unmodified files.
What if my model is thin-walled or hollow?
HiddenMark automatically falls back to a header-only watermark for thin-walled or hollow meshes. The code is embedded in the STL binary header and is still readable by the verifier at proofly.store/hiddenmark.
Which file formats are supported?
Full mesh embedding works for STL files. Header-only watermarks are used for GLB, OBJ, 3MF, FBX, and ZIP packages. All formats sold on Proofly are automatically watermarked at purchase time.
How do I verify a suspicious file?
Upload the file at proofly.store/hiddenmark. The verifier reads the header code in under one second and looks it up in the database — no account required.
Protect your models automatically
HiddenMark is built into every download on Proofly. Upload your model, set your price, and every purchase gets a uniquely stamped copy — no configuration required.