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Print thumbnails: where they come from and why one is missing

Print thumbnails: where they come from and why one is missing


SimplyPrint shows a small picture of each print in Files, in the print queue and on printer cards while a printer prints. This guide covers how to add a missing thumbnail, where the picture comes from, and why the picture on your printer's own screen is a different thing.


In this guide


Add a missing thumbnail

This needs WebGL turned on in your browser. Without it, SimplyPrint shows "WebGL is required to generate thumbnails".


  1. Go to Files.
  2. Right-click the file and choose Generate thumbnail.
  3. Wait for the "Thumbnail saved" message.


Check: the file card now shows the picture. Prints you start from this file show it in the queue and on the printer card.


To take a thumbnail off again, right-click the file and choose Remove thumbnail.


Two different thumbnails

Where you see it

Who makes it

SimplyPrint: Files, print queue and printer cards

SimplyPrint, in your browser, when you upload the file

Your printer's own screen

Your slicer, stored inside the G-code when you slice


Fixing one does not fix the other.


How SimplyPrint gets a thumbnail

Your browser makes the thumbnail while it uploads the file to SimplyPrint:


  • The file carries a picture. SimplyPrint uses it: the largest picture in a G-code file, a 3MF's plate picture, or the picture in an Ultimaker .ufp.
  • The file carries no picture. SimplyPrint draws one from the model (STL, OBJ, 3MF) or from the G-code toolpath. This needs WebGL.


This works the same whether you upload to Files, to the print queue or straight to a printer. It also works when your slicer sends a file to SimplyPrint and the panel opens in your browser to import it, because the panel then uploads it like any other file.


Why a print has no thumbnail

  • The print was started outside SimplyPrint. If you start a file on the printer itself, or send it from another program directly to the printer, SimplyPrint never had the file, so it has no picture to show.
  • The file was added by another tool through the SimplyPrint API. SimplyPrint only stores a thumbnail the uploader sends with the file. Use Generate thumbnail in Files to add one.
  • WebGL is turned off in your browser and the file carries no picture of its own.
  • Printer cards are set to show the printer model. Go to Settings > Printers and turn on Show what the printer is printing. This setting only affects printer cards.
  • The file was uploaded by someone else. Members who may not see thumbnails of files uploaded by others, and may not preview or download them either, do not see those thumbnails on printers, in the queue or in Files. They still see thumbnails of their own files. The permission is called "Can see thumbnails of files uploaded by others".


The picture on your printer's screen

SimplyPrint does not make the picture your printer shows on its own display. Your slicer stores it inside the G-code when it slices. If your printer shows a placeholder:


  1. Open your printer's settings in your slicer.
  2. Find G-code thumbnails. It lists the picture sizes the slicer stores in the file, and has a format setting next to it.
  3. Re-slice the file and upload the new G-code.


Updated on: 27/10/2026

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