Two builds of one website: Kirby vs WP
What we measured and why
it matters.
Rosie Boylan's website currently exists in two forms. The original runs on WordPress, using the Canvas theme and a set of plugins built up over roughly a decade. The replacement runs on Kirby, built from
scratch in 2026.
Both serve the same content — the same words, the same photographs, the same pages. We compared them, what the differences are, and which of those differences a visitor actually feels.
Every number in it was measured directly from the
two live sites, not estimated.
Pages compared
| WP vs Kirby | Wordpress | Kirby | Difference |
|---|---|---|---|
| Files needed before the page can appear | 17 | 5 | 3x fewer |
| Weight of those files (home ) | 1,022 kb | 305 kb | 3.3x lighter |
| Weight of those files (a blog post) | 1,036 kb | 142 kb | 7× lighter |
| Main photograph on the home page | 885 kb | 37kb | 24× lighter |
| Typical photograph delivered | ~ 440 kb | ~ 110 kb | 4x lighter |
Performance
Of course page performance was outstanding. And the new build guaranteed A grade lighthouse scores across all the categories.
10 years is a very long time in web development and the current tooling and optimisation makes these kinds of performance figures fundamental.
Lighthouse Scores
Why I prefer Kirby
First up - Kirby doesn't use a database. It uses a "flat-file" store. Querying databases is slow and using databases exposes a site to mySQL injection attacks. Flat file storage is fast.
Kirby has built in support for all the latest image and templated kinds of content. If custom content is required you can just build versions to support your intent. For example ;
A slider plugin
| WordPress (Slider Revolution) | Ianhobbs swiper | |
|---|---|---|
| Styling | 57 kb | 15.1 kb |
| Scripts | 567 kb | 104.7 kb |
| Total | 624.2 kb | 119.8 kb |
Rosie needed a slider for her site and no slider was available so we built a slider plugin to support her portfolio images.
As we only needed a reduced set of function for the slider we could build a lean custom slider.
You can find it here
We ended up with maintained target speeds of 1 ~ 2 second page loads. There''s lots more to discuss in the rebuild but essentially the migration of sql to flat file was smooth and the whole rebuild and tidying up took about 4 days.
3 pages and about 55 blog posts.
Styleguide
A styleguide for users can help "key" in staff to help land the design concepts used in a site. I had been using a styleguide to map the layouts in our more complex sites. Rosie's stylguide was bundled into the project scope and delivered as a custom static web page outside of the CMS.
The site : https://rosieboylan.com
KirbyCMS : https://getkirby.com/