Images play a key role in creating a strong user experience for your website. However, the number of available image file formats can quickly become confusing. Add technical acronyms into the mix, and the topic can feel overwhelming.
At the same time, choosing the right image format for different parts of your website is not always straightforward. Can formats be used interchangeably? More importantly, how do they affect performance?
Although it may seem complex at first, selecting the right image format becomes much easier once you understand the basics. This guide explains the most common image file types and shows where each one works best.
Let’s dive in.
Does it Matter What Type of Image Format You Use on a Website?
Yes, it does. Image formats directly influence performance, usability, and the speed of your website.
In many cases, large image file sizes slow down load times and make websites feel clunky. As a result, visitors may leave before engaging with your content. On the other hand, using the correct image format keeps your site fast and responsive, which can help improve conversion rates.
Scalability also plays an important role. Certain formats resize more effectively across different screen sizes. By choosing scalable image formats, you create a smoother experience for users on mobile, tablet, and desktop devices.
The Two Types of Image Files
Website images generally fall into two main categories:
- Raster image files
- Vector image files
Raster Image Files
Raster images are made up of pixels, which are tiny dots containing different colours and tones. Together, these pixels form an image. Raster images are common on websites and in print and are usually created through photography or scanning.
Because raster images rely on pixels, they are resolution-based. As a result, stretching them without adjusting resolution leads to reduced image quality.
Common raster formats include PNG, JPEG, and GIF.
Vector Image Files
Vector images use mathematical paths instead of pixels. These paths consist of lines, curves, shapes, and points.
Since vectors rely on formulas rather than resolution, they can scale up or down without losing quality. In addition, they remain sharp across all screen sizes.
Popular vector formats include SVG, PDF, AI, and EPS. These formats work especially well for logos and brand graphics that require frequent resizing.
Popular Image Formats Used by Websites
1. JPEG
JPEG is the most commonly used image format on the web. Developed in 1986 by the Joint Photographic Experts Group, JPEG works best for photographs and images with complex colour gradients.
JPEG files support a wide range of colours while maintaining relatively small file sizes. Because of this, they load quickly and help keep websites fast.
However, JPEGs use lossy compression. This means image quality decreases when files are resized or repeatedly compressed. In addition, JPEG does not support transparent backgrounds. In those cases, PNG is a better choice.
2. PNG
Portable Network Graphics (PNG) is another popular image format for websites. PNG files use lossless compression, which means image quality remains intact after resizing or compression.
Compared to JPEGs, PNGs retain sharper edges and clearer detail. Therefore, they work well for screenshots, graphics, and images with sharp colour transitions.
PNG also supports transparent backgrounds, making it ideal for logos and brand assets. Like JPEGs, PNGs enjoy broad browser support.
3. WebP
WebP is a newer image format developed by Google in 2010. Since then, it has grown in popularity due to its strong compression capabilities.
WebP supports both lossy and lossless compression. As a result, images often have much smaller file sizes without noticeable quality loss. This reduces server load and improves website speed.
In many situations, WebP files are around 50% smaller than PNGs and about 35% smaller than JPEGs. WebP also supports transparency and animation.
That said, WebP has limitations. Browser support is not universal, and some content management systems require plugins or custom setup. Even so, WebP is an excellent option when performance is a priority.
4. SVG
Scalable Vector Graphics (SVG) is a vector image format developed by the World Wide Web Consortium. Like all vector formats, SVG files scale without losing quality.
SVG works best for icons, logos, and simple illustrations. File sizes are usually small, and images remain crisp at any size.
Although most modern browsers support SVG, some CMS platforms require additional configuration. Fortunately, plugins often provide simple solutions.
5. GIF
Graphics Interchange Format (GIF) is widely used for animated images on the web. As a raster format, GIFs support animation and have universal browser compatibility.
However, GIFs only support 256 colours. Because of this, they are not suitable for detailed or static images. In addition, file sizes can grow quickly with animation.
For best results, use GIFs sparingly and only for short animations or simple visual effects.
Less Common Website Image File Formats
While JPEG, PNG, and GIF dominate the web, other formats can be useful in specific situations.
1. APNG
Animated PNG (APNG) works similarly to GIF but supports transparency and 24-bit colour. As a result, APNG files often look better and have smaller file sizes.
However, browser support remains limited. Because of this, APNG is not always suitable for general website use.
2. AVIF
AVIF is a newer format originally developed for video delivery. It offers advanced compression and often produces images that are around 50% smaller than JPEGs.
AVIF supports both lossy and lossless compression, as well as transparency. Despite these advantages, browser support is still limited. Therefore, fallback image formats are essential when using AVIF.
When to Use Each Image File Format
Choosing the right image format depends on how the image will be used.
JPEG works well for photographs, stock images, and product images with complex colours. PNG suits screenshots, graphics, logos, and images that require transparency.
GIFs are useful for short animations and lightweight visual effects. However, they should be avoided for static images.
Wrap Up
Choosing the right image file format is only part of building a great website. High-quality images also need proper optimisation for performance, SEO, and user experience.
As a general rule, use JPEGs for photos, PNGs for graphics and screenshots, and GIFs for short animations.
If you need help optimising images for your mobile responsive website, contact Pixel Fish. We can help you create a fast, user-friendly website that both visitors and search engines love. Contact us to get started.
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