Your website load time has a direct impact on user experience and your Google page ranking. Image file size has a direct impact on your website loading speed. This means that image file size can directly correlate with how many visitors your site sees and the quality of their experience. In short, compressing your image size can help bring more users to your site and keep them there for longer.
In this article, you’ll learn how image compression works and some tips for compressing your images effectively.
How Do You Compress Images?
You compress images using codecs, either directly or through tools that integrate the codecs. Codecs are programs that encode and decode images, video, or audio. These programs allow you to specify the format of media files as well as file properties, like size or quality. There are both proprietary and open-source codecs. The type of codecs you can use depends on the image editing tools you choose to use.
When compressing files, you can choose to use either lossy or lossless compression. Lossy compression combines the pixel data of images, reducing the image size by reducing the overall resolution. Lossy compression permanently eliminates image data but results in much smaller images. It is typically used for websites and other cases where size is more important than quality.
Lossless compression reduces image size assigning duplicate data to variables or parameters which are then referenced to save space. You can also use it to reduce image size by removing unnecessary metadata or header and footer information. With lossless compression, you do not lose any image data but you also cannot compress files as small as with lossy compression. It is typically used for image archiving or when images need to be further processed.
4 Tips for Compressing Images
Now that you understand how compression works and a little about your options, consider the following tips. These tips apply for any compression method you choose.
Compress Images From the Start
Make sure to compress your images before you upload them to your site or any Content Management System (CMS). Compressing before upload enables you to more quickly upload files and reduces your storage needs immediately. If you compress files only after uploading, you are more likely to retain duplicates. You also need to use more storage initially.
Compressing files before upload can prevent you from accidentally using larger images than needed. Since only images with the proper compression are stored, you know that the images you are using are already web optimized. By limiting your selection, you make image assignments faster and easier.
Automate Your Compression
You may not be concerned about automating compression if you only have a few images to manage. If you have to process many images at once, however, automation can save you significant time and energy. It can also help when you need to compress images into several different formats or variations.
Automation enables you to queue large numbers of images and process files when it is most convenient for you. With automation, you can more easily standardize your image compression, naming, and storage location. You can also more efficiently use your resources since automation can be scheduled to occur during low traffic hours.
You can automate image compression with either a custom script or a third-party service. Many services, like Digital Asset Management (DAM) systems or Content Delivery Networks (CDNs), include built-in features for automation. These features can enable you to perform batch processing or create responsive images on demand.
Match Compression to Media Purpose
Most websites don’t require high definition images to deliver a high quality user experience. For these sites, you can use lossy compression without sacrificing noticeable quality. The use of progressive JPEGs can also benefit user experience.
Progressive JPEGs are compressed in a way that allows them to be rendered from low quality to high-quality. Traditional rendering occurs from top to bottom. With progressive rendering, your site will load according to its final layout and sections will not move as images load. This type of loading prevents your site from “jumping around” on users.
You can also dynamically serve a variety of compression formats according to the intended display device. For example, with smaller screens, like mobile devices, you can often use lower definition images than is needed for large desktop monitors. Dynamically serving images requires you to store more image files but can help you ensure the fastest user experience.
Choose Image Formats Carefully
The image formats you choose are what determine the type and ratio of compression you can use. Format also determines the starting size of your images. For example, images saved in PNG format can only be compressed with lossless compression. PNG images start with a larger file size than GIF or JPEG files. In general, JPEG images are the format you should default to for images.
If possible, try to use vector graphics, saved in SVG, CGM, EPS, or XML format. Vector graphics require less storage space to begin with and can be easily compressed. You can use these images to create logos, backgrounds, and other images composed of geometric shapes. These graphics are scalable and retain their quality regardless of size. With vector graphics, you can create responsive websites with a single image file as opposed to creating images for each device specification.
Compressing your images can save you storage space, bandwidth costs, and help you deliver a more enjoyable website experience. Luckily, compression is a process that can be done relatively quickly and easily.
Hopefully, the tips provided here can help you take advantage of the benefits of image compression. If you need help determining where to start, consider these free compression tools.
About the Author
Gilad David Maayan is a technology writer who has worked with over 150 technology companies including SAP, Samsung NEXT, NetApp and Imperva, producing technical and thought leadership content that elucidates technical solutions for developers and IT leadership.