Thumbnail requirements

A good thumbnail is critical to a lesson/course’s success. It should grab the viewer’s attention and help them understand the essence of what the lesson/course has to offer. Following these simple guidelines will ensure that your lesson/course thumbnail is effective and impactful.

Please note: to avoid confusion, each Preptical lesson/course must have its own unique image. The same image should not be used for more than one lesson/course. Textual information such as the name of the lesson/course is not permitted within the thumbnail. Please review the Use of Text section below for more information.

Size and dimensions

Always design your lesson/course thumbnail at the following pixel dimensions.

  • Recommended aspect ratio: 1.67/1
  • Minimum required dimensions: 835 x 500 pixels
  • Maximum required dimensions: none
  • File format must be .jpg, .jpeg, .gif, .bmp, or .png
  • Maximum file size: 2 Mb


A good lesson/course thumbnail enables the viewer to predict what the lesson/course is about. Ensure that the image relates directly to the lesson/course content and is tonally appropriate. 

Use of Text

Do not include textual information or the name of the lesson/course within the image.

Stock Photography

Stock photography can often feel staged, cold, or inauthentic. Only use stock images that feel natural and are high quality.

Specify and Simplify

One of the most important factors of a successful lesson/course thumbnail is simplicity. Use familiar visual concepts that communicate the idea clearly. Try to feature iconic elements that capture the essence of the lesson/course in a simple, unique way. 

Limit the number of visual elements and detail to drive better comprehension. Too many unique elements and too much visual detail will compete for attention and create confusion.

Use of Illustration

Illustrations should be iconic and elemental rather than detailed or cartoony.

Foreground & Background

Only use background images/patterns if they enhance or add to the comprehension of the lesson/course concept rather than repeating it.

Single Point of Focus

Incorporate a central point of focus in your images to draw viewers in.


Images should be clear and non-pixelated.


Avoid applying multiple visual effects or textures to your image.  

Custom Branding and the Use of Logos

You may use your own brand logo in your lesson/course.  Make sure your logo is legible, on brand, has adequate negative space, and is within the content safe area.  Do not add any frames, borders, strokes or letterboxing.