Image optimisation: the website performance work people overlook

Image optimisation: the website performance work people overlook

25 August 2026 · 3 min read

Imagery can give a website confidence and character, but oversized or poorly prepared files can make the same experience slow and difficult to use. Image optimisation is not simply compression at the end of a project. It begins with choosing the right visual, format, dimensions and context for each page.

Choose the image for the job

A large hero photograph, a client logo and a small article thumbnail have different requirements. Start with the largest size the image will actually display at, then create responsive variants for smaller screens. Avoid uploading an original camera file when the browser only needs a fraction of its dimensions. Art direction matters too: a wide desktop crop may hide the important subject on mobile, so test focal points across real layouts.

Use modern formats and sensible compression

Modern formats such as WebP and AVIF can reduce file size while preserving visual quality, although fallback requirements depend on the website and audience. Logos and simple graphics may be better as SVG. Compression should be judged visually rather than pushed to an arbitrary number. The goal is the smallest practical file that still looks credible on the devices people use. Automated processing in the content management system can make this standard consistent.

Write useful alternative text

Alternative text communicates the purpose of an image to people using assistive technology and when the file cannot load. Describe what matters in the context of the page, rather than listing keywords. Decorative images should usually have empty alternative text so they do not add noise. Images that contain important words require special care: wherever possible, present that information as real page text so it remains readable, searchable and adaptable.

Support performance without hiding important content

Images below the visible area can often load later, reducing the work required to display the first screen. The main hero image usually needs different treatment because delaying it can make the page feel slower. Reserve the correct space before an image loads to prevent the layout from jumping. Monitor performance on mobile connections and test complete pages, since several individually reasonable files can still create a heavy experience together.

Create a simple publishing standard

Teams need a practical rule they can follow after launch. Define preferred formats, maximum dimensions, naming conventions, cropping guidance, alternative-text responsibilities and where approved assets are stored. A well-configured WordPress media workflow can automate several technical steps, but editorial judgement still matters. Periodic audits help identify duplicate files, outdated graphics and pages where imagery is damaging speed or clarity.