From websites and social media to marketing materials and presentations, the right picture can make all the difference – which makes understanding image formats and when to pick the right one even more important.

The image format you choose can impact everything from the quality and size of the image file to how it appears on different devices.

With so many options available, selecting the right image format can be daunting.

We’re here to make things easier. Read on as we explain how to choose the best format for your needs.

web designer - choosing the right image format for mobile SEO and page speedUnderstanding image formats

Image formats are essentially the digital packaging of visual content. They determine how an image file is stored, compressed and displayed. Each format uses different algorithms to compress and store data, which results in variations in quality, file size and compatibility.

The existence of multiple formats isn’t just a technological quirk – it’s a response to diverse digital needs. Some formats prioritise high quality for professional printing, while others focus on reducing file size for faster web loading.

Understanding these different needs is key to choosing the right format for your project.

Raster vs. Vector image files

Before looking at specific formats, you need to know about the two main types of image files: raster and vector.

Vector vs raster explained - understanding image formatsRaster images

Raster images are made up of pixels (tiny dots that together form an image). They’re resolution-dependent, meaning their quality is tied to their size. Enlarge a raster image beyond its intended dimensions, and you’ll notice it becomes pixelated – those tiny dots become glaringly obvious and the image appears to be blurry.

Common raster formats include JPEG, PNG and GIF. They’re the ideal choice for complex, multi-coloured images like photos.

Vector images

Vector images, on the other hand, use mathematical formulas to create shapes and lines. This makes them resolution-independent. Whether you enlarge a vector image to fit a billboard or shrink it down to a business card, it remains perfectly clear. This makes vector formats like SVG ideal for logos and any design that requires scaling.

Understanding the core differences between raster and vector images can help you choose the image format for your project, so you get the best quality every time.

Common image formats

Image format types - png, jpg, gif, pdf and svgJPEG/JPG

JPEG (or JPG) is one of the most popular image formats, and was developed by the JPEG organisation. It’s a raster format known for its ability to maintain decent quality while significantly reducing file size through lossy compression (when some of the original data is lost for storage purposes.)

This makes it perfect for website use where quick loading times are crucial for SEO reasons. JPEGs are ideal for photographs and images with gradients.

However, JPEG’s lossy compression means some quality is sacrificed, which isn’t suitable for professional printing or images that require frequent editing.

Did you know… Repeatedly saving an image in JPEG format can also degrade its quality, so it’s best used when final edits are complete.

PNG

PNG is another raster format with specifications held by the W3C. It offers lossless compression, which means it preserves all the original image data. This results in higher quality images compared to JPEG, but they have larger file sizes. PNG supports transparency, making it ideal for images with clear backgrounds or layers.

While PNGs are excellent for web graphics, logos and images that require high detail, their larger file sizes can slow down web page loading speeds. So, they’re best used when quality is a priority over loading speed.

GIF

GIF is a raster format that’s carved out a niche for itself, thanks to its animation capabilities – find more about the standard at W3C. GIFs support up to 256 colours, making them unsuitable for detailed images, but perfect for simple graphics and short animations.

However, the limited colour palette means GIFs aren’t ideal for high-quality images. They’re best used for logos, icons or fun, animated memes.

Did you know… Steve Wilhite, the inventor of the GIF, said the correct pronunciation is with a soft J sound – as in ‘Jif’ – but it’s commonly pronounced with a hard G.

TIFF

TIFF is a raster format known for its versatility and high quality. It’s often used in professional photography and printing due to its ability to store images with minimal compression. TIFF files can be quite large, but they retain all image data, making them ideal for images that require editing and re-saving.

While they’re not suitable for web use due to their size, TIFFs are perfect for archival purposes and professional-grade images.

Read our guide on how to optimise images for SEO.

Specialised image formats

BMP

BMP is one of the oldest raster formats, known for its simplicity and lack of compression. This results in large file sizes, but the format is straightforward to use and widely compatible with various software.

BMP is best used for simple tasks and when file size isn’t an issue. However, it’s largely been surpassed by more efficient formats like PNG and JPEG.

SVG

SVG stands for Scalable Vector Graphics. As a vector format, it excels at maintaining quality at any size, making it ideal for logos, icons and any graphics that need to scale. SVG files are lightweight, which is good for web use.

The ability to animate SVGs also adds versatility, making them increasingly popular in web design and development.

Adobe Illustrator (AI)

Adobe Illustrator files are primarily vector images, stored in the .AI format. These files are perfect for creating graphics that need to maintain clarity at any size, such as logos and illustrations. Illustrator’s vector-based approach allows for precise path control and scalability.

While AI files are native to Adobe Illustrator, they can be exported to other formats like SVG or PDF for broader use. Illustrator is ideal for designers who need high precision and flexibility in their creative projects.

WEBP

WEBP is a modern image format developed by Google, offering both lossy and lossless compression. It combines the best of JPEG and PNG, providing high-quality images with smaller file sizes. This makes WEBP perfect for web use, where both speed and quality are important.

Although it isn’t universally supported yet, WEBP is gaining traction and is a good choice for modern web applications.

Read about the 10 reasons you should redesign your website for SEO.

Online content - choosing the right image can support your websiteHow do I choose the right image format?

Selecting the right image format will depend on several factors:

  • Quality – For high-quality prints, formats like TIFF and PNG are ideal.
  • File size – For web use, smaller file sizes are crucial for faster loading speeds, making JPEG and WEBP great choices.
  • Transparency – When transparency is needed, PNG and SVG are the best options.
  • Use case – Consider whether the image will be used online, in print or as part of a design that requires frequent editing.

Understanding these factors will help guide you in choosing a format that balances quality, file size and functionality.

Choosing the right image format can hugely impact your project’s success, affecting everything from page loading times to visual quality.

By understanding the differences between formats and their ideal uses, you can make your images look great and perform well.

Don’t be afraid to experiment with different formats to find the best fit for your needs.

Submerge can design and build your business a unique, optimised website – find out more about our website design services.