Is my WordPress website too slow? How to find out

A website feels slow when content visibly builds up as the page loads, images pop in late, or your phone takes noticeably longer than your desktop. You can check this in two minutes with Google PageSpeed Insights or the Lighthouse panel in your browser. The most common cause is unoptimised images: uploaded too large, in the wrong format, without sizes that fit small screens. Automate that one corner and you have handled most of the problem.

How to tell your site is slow

The simplest test is your own phone on mobile data, not on Wi-Fi. If the homepage builds up in jumps, the layout shifts, or it takes a while for the first large image to appear, there is work to do. To make it objective, use three free tools: PageSpeed Insights from Google, the Lighthouse tab in the Chrome developer tools, and Core Web Vitals in Google Search Console. All three give you a score and name the biggest bottlenecks.

The usual suspects

In most cases it is a combination of four things, in this order: unoptimised images, slow or oversold hosting, a bloated theme with many fonts and scripts, and missing caching. Images are almost always first, because they account for the largest share of the data transferred by a typical page.

Why images are so often the problem

A stock photo lands in the media library at several megabytes without much effort. WordPress then often serves it in its original format, as JPEG or PNG, instead of a modern format such as WebP or AVIF, which is considerably smaller at the same visible quality. And the phone frequently gets the large desktop version too. Shrinking every image by hand is not something anyone keeps up in day-to-day work.

What you can do about it

The most effective step is to automate image optimisation: every uploaded image is converted to WebP and AVIF on upload, the smallest format is chosen per image, and all image sizes are carried along so the phone gets the right variant. After that you no longer have to think about it. Hosting, theme and caching are the next levers once images are handled.

Where IMG Performer fits in

This is exactly the image corner IMG Performer takes off your hands: automatic WebP and AVIF conversion on upload, locally on your own server, with no cloud service and no account. The free version has no limit. For details on the local approach see the guide GDPR-compliant image optimisation without the cloud, and for a direct comparison with the best-known cloud service see IMG Performer vs. ShortPixel.

Disclaimer

As of September 2026. Details may change; img-performer.enfants.de is authoritative.