What is image compression?
Image compression is a technical process to reduce an image file so that it takes up less space on the website. This is done in a way that affects the quality of the image as little as possible.
Or to put it more precisely Compression reduces image details and sizes by removing some of its header information. The preferred file formats for raster image compression are .png, .jpg, and .gif - each with static pixel color data.
Each of them lets you adjust the quality, level of detail, and size when saving each image. The tradeoff is that each of these "lossy" formats results in image quality degradation.
What are the types of image compression?
Loss-making Compression: Loss-making Compression is a method of Image compression, where parts of the original image are removed to reduce the file size. This method is possibly the most effective form of Image compressionsince it can reduce the largest amount of data. However, there is a disadvantage: since some of the original image information is removed, the quality of the image is affected.
Lossless Compression: Lossless Compression is another method of Image compression, which removes information from the image without affecting the quality of the image. This method of Image compression is less effective than the lossy-Compressionsince it can reduce less data. However, it is more suitable when the quality of the image should be preserved. Therefore, it is often used for secure storage of images.
What are the image formats in image compression?
Here is a table with some important properties of different image formats:
|Image format||Compression type||Quality||Transparency||Animated|
Here is a brief explanation of each column:
- Image format: The image format, for example JPEG, PNG, GIF, SVG or WebP.
- Compression type: Whether the image format is lossy (loss of quality during the Compression) or lossless (no loss of quality during the Compression) is.
- Quality: The general quality of the image. High means that the image is usually of high quality, while low means that the image is usually of lower quality.
- Transparency: Whether the image has transparent areas or not. Yes means that the image has transparent areas, while no means that the image has no transparent areas.
- Animated: Whether the image is animated or not. Yes means that the image is animated, while no means that the image is not animated.
What you should know about image formats:
The different image formats have different properties and use cases. Here is a detailed explanation of the most common image formats JPEG, PNG, GIF, SVG and WebP:
JPEG (Joint Photographic Experts Group)
JPEG is a widely used image format, mainly for photographs and images with a lot of colors and details. It is a lossy compression format that reduces image quality to reduce file size. JPEG does not support transparency and is less suitable for images with sharp edges or text elements.
Typical use cases:
- Realistic paintings or drawings
- Images with many colors and details
PNG (Portable Network Graphics)
PNG is a lossless compression format that works well for images with clean lines, sharp edges, and few colors. PNG supports transparency, which makes it ideal for logos, graphics, and text elements. Because it compresses losslessly, PNG files tend to be larger than JPEG files, but offer higher image quality.
Typical use cases:
- Logos and graphics
- Images with transparency
- Images with text elements
GIF (Graphics Interchange Format):
GIF is an older, lossless image format that supports up to 256 colors. It is best known for its ability to create simple animations. GIF is best suited for small, simple images or animations with limited colors. It also supports transparency, but only in the form of binary transparency (that is, a pixel is either completely transparent or completely opaque).
Typical use cases:
- Simple animations
- Small graphics or symbols
- Images with limited colors
SVG (Scalable Vector Graphics):
SVG is a vector format based on XML that is ideal for scalable graphics. Unlike raster graphics, which consist of pixels, vector graphics are defined by mathematical formulas that describe lines and curves. This allows SVG images to be scaled without loss of quality. SVG is great for logos, icons, diagrams and illustrations that need to be displayed in different sizes.
Typical use cases:
- Logos and symbols
- Diagrams and infographics
- Illustrations needed in different sizes
WebP is a relatively new image format developed by Google that offers both lossy and lossless compression. It allows for smaller file sizes while maintaining quality compared to JPEG and PNG. WebP also supports transparency and animation. However, browser support for WebP is not yet as extensive as for JPEG and PNG, so it may be necessary to use alternative formats for older Browser to provide.
- Illustrations and graphics with transparency
- Animations that require a higher color palette than GIF
In summary, it's important to choose the right image format for your needs to achieve the best balance between quality and file size. JPEG is best for photographs and images with a lot of detail, while PNG is ideal for graphics with transparency and text elements. GIF is good for simple animations and images with a limited color palette. SVG is the best choice for scalable vector graphics such as logos and diagrams. Finally, WebP offers excellent compression and quality for various use cases, but browser support is not yet as widespread as for the other formats.
When choosing the right image format for your website or project, carefully consider quality, file size, and compatibility requirements. Also consider the target audience and the devices on which your images will be displayed to ensure the best user experience.
Image compression offers many advantages. It reduces the size of the image and allows files to be transferred and stored faster. This allows users to store more images on their devices.
Other advantages of Image compression are::
- Faster loading time: Compressed images load faster, which means your page loads faster. This is important because fast loading times are important for users and search engines.
- Reduced data transmission: Compressed images consume less data, making them more accessible to users with slower internet connections.
- Better condition for SEO: Search engines prefer fast, well-optimized pages. If your page loads fast and contains well-optimized images, this will improve your SEO ranking.
- Space saving on the server: Compressed images take up less space on the server, which means you need less storage or pay less for storage.
Image compression also has some disadvantages. Although the Compression mostly reduces the file size of an image, it can affect the quality of the image.
Other disadvantages of Image compression are::
- Quality loss: Although modern image compression methods usually do not visibly affect the quality of images, in some cases there may still be a slight loss of quality. As a rule, the more the image is compressed, the greater the quality loss.
- Time requiredIt can take some time to compress images, especially if you have a lot of images on your site. However, there are many tools and plugins that automate the compression of images to minimize the time required.
- Restrictions on certain file types: Some file types, such as GIFs, are already heavily compressed and cannot be compressed further without visibly degrading quality. In such cases, compressing does not bring any benefits.
- Cost of special tools: There may be costs for special tools or plugins that help you compress images. However, there are also many free options that you can use.
Image compression is commonly used in the following use cases: Websites, digital photography, video and image editing, video streaming, and image archiving.
Example 1: JPEG
JPEG (Joint Photographic Experts Group) is a commonly used image compression format. It uses a unique algorithm to reduce the file size of an image without affecting the quality of the image.
Example 2: PNG
PNG (Portable Network Graphics) is another commonly used image compression format. It uses a lossless compression algorithm to reduce the file size of an image. This does not affect the quality of the image.
How does image compression affect SEO?
As you probably already know, website load times are a very important factor when it comes to the Ranking goes. One way to check all image sizes and for the Compression to highlight to speed up website and page load times and make the end user more satisfied is the use of Pagespeed Insigths.
10 tips how to optimize your images:
- Name your images clearly and in plain text: It is important that you give your images meaningful and descriptive names so that they can be easily understood and recognized by search engines. Avoid using only numbers or special characters, as this is not very meaningful.
- Optimize your alt attributes carefully: Alt attributes are descriptions of images used in HTML code. They are important because they help search engines understand the image and describe its content. Make sure that you choose your alt attributes carefully and that they contain a meaningful description of the image.
- Choose your image dimensions and product angles wisely: It's important to choose the right image dimensions and angles for your products to ensure they are clearly visible and show all the important details. Avoid using images that are too small or unclear.
- Reduce the file size of your images: Large image files can contribute to your page loading slower. To ensure that your images load quickly, try reducing their file size by compressing them or adjusting the quality level.
- Choose the correct file type: There are different image formats that are suitable for different purposes. Choose the right format for your images to ensure they have the best possible quality and load quickly.
- Optimize your thumbnails: Thumbnails are small preview images displayed on your page to give users an idea of the images available. Make sure your thumbnails are highly visible and of high quality to entice users to click on them.
- Use image sitemaps: One imageSitemap is a special type of Sitemap, which was created specifically for images. It helps search engines find and index your images by providing information about the images, such as the image title, image description, and imageURL. By selecting an imageSitemap you can make sure that your images are found by search engines and that they are indexed be
- Avoid superfluous images: While decorative images usually don't contain important information, they can still help your page load slower. Make sure you use decorative images only when they're really necessary, and possibly use CSS styles to add visual elements instead.
- Be careful when using content delivery networks (CDNs): CDNs are networks of servers designed to deliver content like images faster by storing them on servers near the user. While CDNs usually help images load faster, they can also cause your page to load slower if they are not configured properly. Make sure you configure and test your CDN carefully to ensure that it doesn't slow down your site.
- Test your images!: It's important to test your images regularly to make sure they load properly and are of high quality. Use tools like PageSpeed Insights or Lighthouse to see how fast your images are loading and make sure they are highly visible and of high quality.
Typical mistakes with image compression in SEO
- Use of inappropriate compression methods: Use of inappropriate compression methods may result in images being either over-compressed or under-compressed, resulting in degraded image quality. It is recommended to use suitable compression methods such as lossless or lossy compression to achieve optimal image quality with small file size.
- Unadjusted compression ratio: Unadjusted compression rate can cause images to be either over-compressed or under-compressed, resulting in degraded image quality. It is recommended to adjust the compression rate to the type of image and purpose of use to achieve optimal image quality at a small file size.
- Use of unsupported formats: Using unsupported formats may cause the images not to display correctly and thus affect the usability of the page. It is recommended to use common and supported formats such as JPEG or PNG to ensure compatibility.
- Lack of scaling: Lack of scaling can cause the images to be too large and thus affect the page load time. It is recommended to scale the images to the required size before compression to optimize the loading time.
- Lack of optimization: Lack of optimization can cause the images to be unnecessarily large and thus affect the page load time. It is recommended to optimize the images before compression, for example by removing unnecessary Metadata removed or the color depth reduced.
WordPress plugins for image compression
- WP Smush: This Plugin automatically optimizes the images during upload by removing unnecessary Metadata removed and the image size reduced. It supports bulk smushing, which means that it can optimize all images at once and has a built-in function to monitor disk space usage. A disadvantage could be that it does not support PNG images with transparent background and it can lead to quality loss.
- EWWW Image Optimizer: This Plugin automatically optimizes the images when uploading and also supports optimization of already uploaded images. It supports optimization of PNG, JPG and GIF images and uses various optimization tools such as jpegtran, optipng and gifsicle. However, it may cause longer loading times when uploading images.
- ShortPixel Image Optimizer: This Plugin automatically optimizes the images when uploading and also supports optimization of already uploaded images. It supports optimization of PNG, JPG and GIF images and can also optimize PDF files. It also offers the possibility to optimize the images in the Cloud which can reduce the server load. A disadvantage could be that it offers a limited number of free optimizations per month.
- Imagify: This Plugin automatically optimizes the images when uploading them and also supports the optimization of already uploaded images. It supports the optimization of PNG, JPG and GIF images and offers three different compression levels: normal, aggressive and ultra. It also offers the possibility to optimize the images in the Cloud which can reduce the server load. A disadvantage could be that it offers a limited number of free optimizations per month.
- Kraken.io: This Plugin automatically optimizes the images when uploading them and also supports the optimization of already uploaded images. It supports the optimization of PNG, JPG and GIF images and also offers the possibility to optimize the images in the Cloud which can reduce the server load. It also offers the possibility to view the images directly from the API which can reduce the server load. A disadvantage could be that it offers a limited number of free optimizations per month and it can lead to quality loss.
Other platforms and solutions for image compression
- TinyPNG: This is an online platform that allows compressing PNG and JPEG images. It uses advanced algorithms to reduce the image size without compromising the image quality. An advantage of TinyPNG is that it is easy to use and requires no installation, it can also upload multiple images at once. A disadvantage could be that it doesn't support other image formats such as GIF and TIFF.
- Compressor.io: This is another online platform that allows compression of PNG, JPEG and GIF images. It also offers the possibility to compress the images in the Cloud to optimize, which can reduce the server load. An advantage of Compressor.io is that it has a preview function that lets you see the effects of the optimization on the image quality before saving it. A disadvantage could be that it doesn't have support for other image formats such as TIFF.
- Adobe Photoshop: Adobe Photoshop is a professional image editing software that also offers the possibility of compressing images. It offers various tools and options to reduce the image size without compromising the image quality. One advantage of Photoshop is that it offers a wide range of tools for image editing, as well as support for almost all image formats. A disadvantage might be that it is an expensive purchase and it has a bit of a learning curve to fully utilize its features.
- ImageOptim: This is a free Mac application that allows compressing PNG, JPEG and GIF images. It uses various optimization tools such as pngcrush, jpegoptim and gifsicle. An advantage of ImageOptim is that it has a simple and intuitive interface and it does not require installation. A disadvantage might be that it's only available on Mac and it doesn't offer support for other image formats like TIFF.
- RIOT (Radical Image Optimization Tool): This is a free image optimizer available for both Windows and Mac. It supports optimization of PNG, JPEG and GIF images. RIOT offers a preview function that lets you see the effects of the optimization on the image quality before saving it. It also offers several options such as the ability to manually set the compression level and the ability to keep the image's meta data. A disadvantage could be that it doesn't offer support for other image formats like TIFF and it can cause quality loss.
Image compression is a useful method for reducing the file size of images without compromising the quality of the image. It offers many advantages such as reducing file size and allowing faster transfers and saves. However, it may also have some disadvantages such as degrading image quality and creating artifacts. Therefore, it should be used carefully.« Back to Glossary Index