Image formats – what and why?

Image formats for building websites. The use of image files is crucial when building websites, as visual elements contribute significantly to the user experience. There are several types or formats of image files that can be used to optimise upload speed and image quality. In this article, we will focus on some of the most commonly used image file types, their advantages and disadvantages.


JPEG (Joint Photographic Experts Group)

JPEG is the most common type of image file used on websites. This format allows image compression, which reduces the file size and consequently the image upload time. JPEG is ideal for photos and images with many colour gradients. However, JPEG does have some drawbacks, such as loss of image quality with multiple storage or compression.


– Efficient compression of images, reducing file size.
– Suitable for photos and images with many colour gradients.
– Supports a full range of colours.

– Loss of image quality with multiple storage or compression.
– It is not suitable for images with sharp geometry or transitions between solid colours.


PNG (Portable Network Graphics)

PNG is an image file format often used for web pages. This format allows lossless compression of images, which means that no image quality is lost during storage or compression. PNG is ideal for images with sharp geometry, transitions between solid colours and images with backgrounds that need to be transparent. The disadvantage of PNG is the larger file size compared to JPEG, which can affect the loading speed of the image.

– Lossless image compression, preserving image quality.
– It supports transparent backgrounds, ideal for icons and images with transitions.
– Suitable for images with sharp geometry and transitions between solid colours.

– Larger file size compared to JPEG, which can affect the speed of image upload.

GIF (Graphics Interchange Format):

GIF is an image format often used for animations or short videos on websites. This format supports animations with multiple consecutive images. GIF uses lossless compression, but has a limited colour gamut and is not suitable for complex images or high-quality photos. In addition, GIF files tend to take up more space than other formats.

– It supports animations and short videos.
– Lossless image compression.

– Limited colour gamut, not suitable for complex images or high quality photos.
– Files take up more space than other formats.



WEBP is a relatively new image file format developed specifically for web use. WEBP combines the advantages of JPEG and PNG formats, providing both image compression and background transparency support. The WEBP format has a smaller file size compared to PNG and JPEG, which contributes to faster image loading. However, older browsers and operating systems may not support this format.

– Efficient image compression.
– Supports transparent background.
– Smaller file size compared to PNG and JPEG.

– It may not be supported in older browsers and operating systems.


SVG (Scalable Vector Graphics) vector graphics

It is a vector format, which means that images are based on mathematical formulae and geometric shapes instead of pixels. This allows images to be resized without loss of quality, which is particularly useful for responsive websites with different devices and screens.

– Small file size: SVG files are typically smaller than other image formats such as JPEG or PNG. This means that images load faster, which improves the speed of web pages. Smaller file sizes also reduce bandwidth consumption and server load.
– Preserving quality on zoom: due to its vector nature, the SVG format preserves image quality even when zoomed. This is especially important if you want to use icons or graphics that can be displayed to users in different sizes.
– Editable and customisable: SVG files are text files, allowing you to edit and customise the content using common text editors or specialised tools. This makes it easier for designers and developers to customise images and create interactive graphics and animations.

– Processing complexity: because SVG files are vector, they can contain complex geometric shapes and details. This can require more computing resources and processing time, especially for larger or more complex images. On older or less powerful devices, they may appear slower.
– Browser support: although support for the SVG format is widespread, there is a possibility that older browsers may not support all functionality or display SVG images correctly. Compatibility with target browsers should be checked before using SVG files.
– Not suitable for complex photos: while SVG is great for vector graphics and icons, it’s not the best choice for complex photos or images with lots of colour gradients. For such images, it would be better to use other formats such as JPEG


Choosing the right type of image file formats for a website depends on the type of image you want to display and your loading speed needs. JPEG is suitable for photos, PNG for images with sharp geometry and transparent backgrounds, GIF for animations, while WEBP combines the advantages of both formats. SVG is great for displaying vector graphics, but is unsuitable for photos. Consider the advantages and disadvantages of each format and choose the most suitable one for your website’s needs. You can also read more about the pictorial material here:

Bit or vector notation?
Using and preparing image material in graphic design


Tomaž Berčič