Image compression reduces the data required to deliver an image while retaining appropriate visual quality. It works alongside correct dimensions, responsive variants and format selection. Compressing a large original helps, but sending a much smaller screen an unnecessarily large image can still waste bandwidth and delay useful content.
Link image work to measured experience
Images often contribute substantial page weight and can affect Largest Contentful Paint when a prominent image is the measured element. File size is only one part of the delay: late discovery, server response and rendering can also matter. Compression is therefore a means of improving delivery, not a direct ranking switch. Maintain enough detail for the image’s purpose, especially product features, diagrams and text within supplied graphics. A tiny but unreadable image undermines the reason for including it.
Compare candidates at their actual size
Inventory the heaviest images on important templates and record displayed dimensions, source dimensions, format and transferred bytes. Generate appropriate variants and compare them visually on high-density and ordinary screens. Check transparency, colour, fine detail and small lettering. Confirm that the browser selects a sensible responsive source rather than downloading the largest original. Preserve relevant alt text and explicit layout dimensions when replacing files. Measure the page again after deployment to confirm that the selected optimisation affects the observed bottleneck.
Check existing links to replaced images where the full-size file is shared directly. Renaming or deleting those originals may break useful references, so consider their role before changing the asset workflow.
Protect useful detail in a project gallery
Suppose a Perth cabinetmaker uploads full-resolution photography directly from a camera. A gallery thumbnail rarely needs the same resource as a detailed project view. Producing separately sized variants can improve delivery while retaining a larger version where close inspection is useful. Review material textures and edge details before approving compression. If the first hero is still late, investigate how it is loaded instead of repeatedly reducing quality. Document the publishing workflow so future uploads receive the same treatment automatically.
Image delivery can be assessed as part of technical SEO performance work.
Common questions
Is the smallest file always best?
No. Choose an acceptable visual result for the purpose and display size. Over-compression can damage text, product detail and confidence in the page.
Should I change every image to one format?
No. Photography, transparency and line art have different needs. Compare suitable formats and retain compatibility through an appropriate image delivery setup.
Terms in this guide
- Largest Contentful Paint — A loading measure that reports when the largest visible content element is rendered. Large hero images, slow delivery and render-blocking resources can delay it.
- Alt text — A text alternative that describes an image’s relevant content or purpose. Decorative images can use an empty alternative. It should describe the image naturally rather than repeat keywords.
- Responsive design — A layout approach that adapts content and controls to different screen sizes, input methods and viewing conditions.
- Lazy loading — Deferring an asset until it is approaching the area the visitor is viewing. Main above-the-fold imagery should be prioritised rather than delayed unnecessarily.
Related SEO guides
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