The proportional relationship between the width and height of an image. It's written as a formula (e.g., 16:9 or 1:1) and determines the image's shape, not its actual size in pixels. Why it matters: Using the wrong aspect ratio causes platforms to awkwardly crop your images, potentially ruining your composition.

The fundamental process of reducing an image's file size (its total number of bytes) to save storage space and, more importantly, increase website loading speed. There are two main approaches: Lossy (which strategically discards data) and Lossless (which preserves all data).

A compression method that permanently removes some image data to achieve a significantly smaller file size. File Types: JPG and the 'lossy' mode of WEBP. It's ideal for photographs and complex images where a tiny, imperceptible loss in quality is a worthwhile trade-off for a huge performance gain.

A compression method that reduces file size without losing a single bit of the original image data. The image can be perfectly reconstructed to be pixel-for-pixel identical to the source. File Types: PNG and GIF. It's essential for logos, icons, and graphics that must maintain sharp lines and perfect clarity.

The smallest single point or 'dot' of color in a digital image. Every photo you see on your screen is made up of millions of these colored dots. Why it matters: The total count of pixels dictates an image's resolution and, thus, its potential file size.

The detail an image holds, typically expressed as its total width and height in pixels (e.g., 1920x1080). Higher resolution means more detail but also a much larger file size. Recommendation: For the web, always aim for the resolution you need, not the maximum resolution available.

The specific standard and encoding method used to store image information in a computer file. Common formats include JPG, PNG, and WEBP. Why it matters: Each format has unique strengths (like JPG for color depth or PNG for transparency) and choosing the wrong one can severely impact quality or file size.

An additional channel within an image file that defines how opaque or transparent each individual pixel is. File Types: PNG and WEBP support this critical feature, allowing for images with non-rectangular shapes, perfect for logos that need to float cleanly over any background color.