Start with the images that matter most
Images help explain products, illustrate instructions, and make pages easier to use. They can also account for a large share of a page’s download size. Optimization is not simply making every file as small as possible: an image that looks blurry or hides useful detail can make the page less helpful. The goal is to deliver enough visual quality for the image’s purpose without making visitors download unnecessary data.
Begin with a few representative pages, such as a homepage, an article, and a product or service page. Look for oversized hero images, repeated thumbnails, background images, and files that are much larger than they appear on screen. Prioritize images that visitors see immediately and images reused across many pages. This gives you a manageable starting point instead of trying to revise an entire image library at once.
Match file dimensions and format to the job
Export images at dimensions appropriate for where they appear. A small card thumbnail rarely needs the same pixel dimensions as a full-width banner. Account for sharper screens by providing sufficiently detailed versions, but avoid sending the largest original file to every device. If an image contains text or fine details that must remain legible, check it at the sizes people will actually see.
Choose formats according to the content. JPEG is often suitable for photographs; PNG can be useful when transparency or lossless detail is important. WebP and AVIF may produce smaller files for many images, though results vary with the source and compression settings. SVG works well for simple graphics such as logos and icons when the file is appropriate and safely prepared. Compare a few exports visually rather than assuming that one format or quality setting is best for everything.
Compress exported files and remove unnecessary metadata where practical. Keep an editable original so you can generate new sizes later without repeatedly recompressing an already degraded copy. Meaningful filenames can help your team manage assets, but renaming a file alone will not compensate for an excessively large download.
Send different image sizes to different screens
Responsive images let the browser select a suitable file instead of forcing a phone to download an image intended for a wide desktop layout. In HTML, srcset can list available image widths, while sizes describes how wide the image is expected to appear under different layout conditions. A picture element can offer alternative formats or crops when the design calls for them. These tools work best when their declared sizes match the actual layout, so check the page at several viewport widths.
Set width and height attributes, or reserve space with CSS, so the layout does not jump when an image arrives. For images managed by a content management system, check whether it already generates multiple sizes and whether templates use them correctly. Uploading a smaller file helps, but it does not fix a template that routinely selects the wrong variant.
Load images when they are needed
Images far below the initial viewport are reasonable candidates for lazy loading. Images central to the first screen, especially a prominent hero image, generally should not be delayed. If that image is a likely largest visible element, make its file easy for the browser to discover and avoid hiding it behind unnecessary scripts. Use loading and priority settings deliberately rather than applying the same setting to every image.
Consider the rest of the delivery path, too. Appropriate browser caching can prevent returning visitors from downloading unchanged files again. If you change an image but keep a long cache lifetime, use a new asset URL or a versioned filename so visitors receive the update. Decorative CSS backgrounds can be useful, but an important content image is usually easier to describe, size, and load predictably as an image element.
Check speed without losing usefulness
After making changes, compare the same pages under similar conditions. Browser developer tools can show image file sizes, selected responsive variants, and when requests begin. Page-speed tools can flag potential issues, but inspect the page yourself on both a narrow screen and a larger one. A lighter file is only an improvement if its crop, clarity, and placement still serve the visitor.
Keep image accessibility separate from compression. Informative images need concise alternative text that conveys their purpose; decorative images may need empty alternative text so they do not add noise. Review captions or nearby explanations when visual detail is essential. An effective workflow is repeatable: identify a heavy image, prepare suitable versions, confirm the browser receives the right one, and check that the finished page remains clear and stable.
