Downloaded file size and resolution (megapixels) are two separate items.

Images in most modern formats are compressed, including JPEG, PNG, WebP, AVIF, JPEG-XL, HEIF, and more.

PhotoCircle uses JPEG, which is the most common format, along with advanced compression techniques to reduce the overall byte size of the image files, while maintaining pixel resolution and image quality.

What matters is the image resolution, which can be calculated by multiplying the two numbers in the “Dimension” information of a photo's file together.

For example, a photo may be less than 1 MB when downloaded but its dimensions (4032 x 2688) when multiplied together would mean it is 10.8 megapixels (10,838,016 pixels).

For more information on image compression, please refer to: https://www.cloudflare.com/learning/performance/glossary/what-is-image-compression/