In this case, do I need a paid version?

I have been uploading files to Cesium ion and then downloading and using the tiled files. Is there a difference in the result files between the free version and the paid version? I am currently using the free version, but I am having difficulty with rendering. (Rendering has stopped. drawingBufferWidth must be greater than zero error occurred)

Hi, welcome to the Cesium community.

There is no difference in the tiling and rendering between the free and paid versions of Cesium ion. If you are having trouble with rendering, are you able to provide a simplified sandcastle that illustrates the problem?

You may need a paid version depending on what you are using Cesium for, and how much you are using it. The paid version gives you higher data limits, and is required for types of usage (like commercial use). The free community plan is available for personal and exploratory projects, and comes with lower data limits. See the Cesium pricing page for more details. Please feel free to reach out if you have any questions about this.