STL — The Universal Standard
STL (STereoLithography) has been the default 3D printing format since the 1980s. Every slicer — PrusaSlicer, Cura, Bambu Studio, Chitubox — reads it without issues. Every buyer who has ever touched a 3D printer knows STL.
Why it wins for sellers: Zero compatibility risk. A buyer on any machine, any country, any skill level opens an STL without confusion. This reduces refund requests.
Downsides: STL files are uncompressed triangle meshes with no color, no material, no embedded metadata. A complex model can be 50–200 MB. No way to include recommended print settings. The format carries no notion of intended scale (mm/inch confusion is real).
HiddenMark support: Full. Proofly embeds a unique per-buyer watermark into the vertex positions — invisible to the buyer, permanent in the file. If a leak happens, you can identify the exact download within seconds.
3MF — The Modern FDM Choice
3MF (3D Manufacturing Format) was designed to replace STL for FDM printing. It is a ZIP archive containing geometry, materials, color, and print metadata — all in a single file.
File size advantage: 3MF compresses mesh data. A 45 MB STL frequently becomes a 12–18 MB 3MF — 50–70% reduction without any quality loss. Smaller downloads mean happier buyers and lower storage costs.
Metadata advantage: You can embed recommended layer height, supports, and material type directly in the file. Buyers using PrusaSlicer or Bambu Studio see your settings pre-loaded — no guesswork, fewer failed prints, better reviews.
Compatibility: All major 2026 slicers support 3MF. Older or niche slicers may not. For maximum reach, pair 3MF with an STL in a ZIP package.
HiddenMark support: Full. The watermark survives reslicing and format conversion.
GLB — Best for Visual Sales Pages
GLB (binary glTF 2.0) is built for real-time 3D rendering: it supports PBR materials, textures, animations, and morph targets. It is what powers most WebGL viewers — including Proofly's in-browser viewer.
Why it matters for conversions: A listing with a fully textured, material-rich GLB preview looks dramatically better than a flat-grey STL render. Buyers can inspect the model from every angle in the browser, with correct colors and surface finishes. This directly increases add-to-cart rates for visualization and game-dev models.
When not to use GLB as your only file: GLB is not a print format. Slicers do not read GLB. If you are selling print-ready models, always include an STL or 3MF — GLB should be an additional preview file, not the primary download.
HiddenMark support: Full. Watermark is embedded in mesh geometry, not in textures or materials, so it persists through material edits.
OBJ — The Universal 3D Interchange
OBJ (Wavefront Object) is a plain-text mesh format that pairs with a .mtl material file. It is the lingua franca of 3D modeling — every major 3D application (Blender, Maya, Cinema 4D, ZBrush) reads and writes OBJ without a plugin.
Best use case for sellers: Game assets, render-ready scenes, and any model that will be opened in a modeling application rather than a slicer. OBJ preserves UV maps, material zones, and multiple objects in one file.
Downsides: The .mtl sidecar file requirement means a buyer who only downloads the .obj gets geometry without materials. Always ZIP obj + mtl + textures together to avoid buyer confusion.
HiddenMark support: Full. The watermark is embedded into vertex positions, which are preserved through OBJ import/export cycles.
The Seller's Format Strategy for 2026
The highest-converting Proofly listings follow this pattern:
- Print-ready models: ZIP containing STL + 3MF. STL for compatibility, 3MF for print settings and smaller download. Use a GLB as a preview attachment for a better listing thumbnail.
- Game-dev / visualization assets: GLB as the primary file, OBJ as a secondary. GLB gives buyers an instant browser preview; OBJ covers import into modeling tools.
- Multi-format packs: ZIP with STL + 3MF + OBJ + GLB. Maximum reach, one purchase. Each format gets a unique HiddenMark fingerprint — if any version leaks, you trace it.
Proofly lets you upload a single ZIP containing all formats. Buyers download everything in one click, and every file in the archive receives its own invisible watermark.