Errors when loading a file
| What you see | Likely cause | What to do |
|---|---|---|
| “…looks like a binary file, not text G-code” | The file is binary or packaged, such as PrusaSlicer’s .bgcode or Bambu Studio’s .gcode.3mf. An .nc file can also be a binary NetCDF data file rather than a CNC program (see the NC file viewer). | Export a plain-text .gcode file from the slicer. See how to open G-code files. |
| “This file is empty” | A zero-byte file, often from an interrupted export. | Export the file again. |
| “…larger than 150 MB” | The file is above the viewer’s size limit. | Reduce the file size at the source: slice fewer objects per file, increase curve tolerance, or use arc output if your slicer and printer firmware support it. |
| “…more movements than the browser viewer can hold” or “…more toolpath segments…” | The file is under 150 MB but has more than 2.5 million movements, or would draw more than 2.5 million segments (arcs are split into short chords, which adds segments). | Use a smaller file, or split the job. |
| “The browser ran out of memory” | Large files need a lot of RAM. | Close other tabs, use a computer rather than a phone, or use a smaller file. |
| “G-code commands were found, but no movement commands” | The file has setup commands but no G0, G1, G2 or G3 moves, or it is a macro or configuration file rather than a toolpath. | Check that you opened the job file, not a config or macro file (some firmware also uses .g for those). |
| “Interactive 3D needs WebGL…” | WebGL is unavailable or disabled in the browser. | Turn on hardware acceleration or try another browser. Statistics, bounds and the source list still work. |
The file loads but looks wrong
| Symptom | Likely cause | What to do |
|---|---|---|
| Part of the toolpath is missing | Commands the viewer cannot interpret reliably are skipped: canned cycles (G81–G89), splines (G5), parameters and expressions (#100, [1+2]). | Open the parser notes, which list each skipped command and its line numbers. For drilling, try a post-processor option that outputs plain moves. |
| The path differs from the real job | G51 or G68 scaling or rotation, tool offsets (G43) or cutter compensation (G41/G42) are not applied. | Compare with your CAM preview; the viewer shows the programmed path. |
| A 4th- or 5th-axis program looks flat or wrong | A, B and C words are ignored without a warning, so only X, Y and Z movement is drawn. | Use rotary-capable software to check that program. |
| No layers are listed | Spiral or vase mode, no layer comments, or Z changing on almost every extruding move. More than 20,000 distinct Z levels is also treated as not layered. | Expected for vase mode. The layer note under the playback controls says why. |
| Everything is drawn as travel, or the labels look wrong | The profile is wrong, or the moves carry no extrusion values. | Switch the Profile selector between 3D printing and CNC / milling. The profile only changes labels and colours. |
| The size looks wrong by 25.4× | Inch and millimeter mix-up. | Set the Units selector to match your file (G20 inches, G21 millimeters). |
| The bounds are bigger than the part | Bounds describe where the tool moves, including travel and lead-ins, not the finished part. | Read them as the tool’s reach, not part dimensions. |
| No line leads in from the home position | G28 homing is recognized but not drawn, and the viewer does not invent a line from an unknown starting point. | Expected behavior. |
| A file with an unusual extension is accepted | The extension is only a hint; the contents decide. | None needed. |
Still stuck?
Email the address on the contact page with your browser, the kind of file and what you expected to see. Please do not attach private G-code files. You can also try the online G-code viewer again with a smaller or re-exported file.