What size should I use for the featured blog image?

The blog’s featured image will be displayed in full-width browsers at 708 pixels wide x 472 pixels high. 

• To make sure your image is displayed crisply on high-resolution displays, we recommend you upload an image that's twice that size: 1416 pixels wide x 944 pixels high.
• Uploading an even larger image is fine, too: our system will automatically shrink it. 
• If the proportions of your image differ from the proportions of the space, the image will be cropped to fit the proportions.  
• If you upload a smaller image, it will be "upscaled" to fit the space, but will look blurry, depending on how small it is and the device being used.    
• To make sure your website loads quickly, we recommend using JPEG images. (And in case you're wondering, the number of dots per inch — or dpi — is irrelevant. Anything's fine.)