«The site is slow» means different things depending on who says it: the first page takes ages to appear, the admin panel drags, or a site that used to be fast no longer is. The causes differ and so do the fixes — which is why the first thing to do is not to install anything, but to measure.
Measure first, touch things afterwards
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Open the site on another network. From your phone on mobile data, for instance. If it is fast there, the problem is your connection or your browser cache — not the site.
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Try a second page. If only one is slow, the problem is that page — a gallery, a map, a form — and not the server.
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Notice whether it is only the dashboard. A slow /wp-admin with a fast site is nearly always a plugin, not a shortage of resources.
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Write the numbers down before you start. Change one thing at a time and measure again. Changing five things at once may well work — but you will not know which one it was, and next time you start from scratch.
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The most common cause here: the PHP version
It is the one we see most and the cheapest to fix. Plenty of sites are still running PHP 7.2, which stopped receiving fixes in November 2020, or PHP 7.4, frozen since November 2022. PHP 8 runs the same code noticeably faster — and, unlike the others, still gets security fixes.
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In cPanel, search for MultiPHP Manager or Select PHP Version.
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Open the site and the dashboard straight after, and click through a few pages. That is the test that counts.
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Change it, test it, and know how to go back. A very old theme or plugin may not run on PHP 8 — and then the site errors instead of getting faster. It is not serious: you switch back on the same screen and everything is as it was. Make the change at a quiet hour, not at 11am on a Monday.
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Caching: our servers run LiteSpeed
Without caching, every visit makes the server build the page again — query the database, run the PHP, assemble it all. With caching, the finished page is served directly. It is the single change that cuts response time most.
Our servers run LiteSpeed. That matters because it means the right plugin for WordPress here is LiteSpeed Cache: it stores the pages in the server itself, before PHP even starts — something generic caching plugins cannot do.
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Install the LiteSpeed Cache plugin from the WordPress repository.
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Turn caching on. The default options already give you most of the gain — you do not need to touch everything.
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After any change to the site, use Purge All. If you edited a page and still see the old one, that is the cache doing its job.
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| Caching fixes |
Caching does NOT fix |
| Pages that repeat |
Pages that differ per visitor — cart, account, checkout. Those have to be excluded. |
| Traffic spikes |
The admin dashboard, which is never cached. |
| An overloaded server |
A page that is slow in itself — if it takes 8 seconds to build, the first visit still takes 8. |
Images: nearly always the biggest single win
The most common reason for a heavy page is not the code — it is photographs uploaded exactly as they came off the camera. A 4 MB image on a page that displays 800 pixels wide makes every visitor download 4 MB to see 800 pixels.
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Resize before uploading. For most sites 1600 pixels wide is more than enough.
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Save as WebP where you can: it usually comes out half the size at the same visible quality.
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Turn on lazy loading — images load only when the visitor reaches them. LiteSpeed Cache has that option built in.
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Plugins and themes
Every active plugin costs something on every page, even the ones that do not use it. It is not the number that counts — it is the weight of each one.
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Deactivate what you do not use, and delete what is deactivated. A deactivated plugin does not run, but it is still an unpatched door.
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Be suspicious of three families: heavy page builders, statistics plugins that write every visit into your database, and homepage sliders.
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To find the culprit: deactivate half, measure, and repeat with the half that remains. Four or five rounds get you there.
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The database
Over the years invisible rubbish piles up: a revision of every text ever edited, data from plugins removed long ago, and options loaded on every page. On a site with a few years behind it, clearing this out gives a real gain. Do it with a copy saved first — see how to restore your data with JetBackup — and for direct management, creating databases and using phpMyAdmin.
When it is not the site, it is the plan
There is a point past which optimising stops paying off. If Resource Usage shows the limit being hit every day, or if error 508 appears, the site no longer fits the plan — see website errors: 500, 403, 404 and 508. At that point the honest answer is a bigger plan and not more squeezing: shared hosting vs VPS: which one does your project need.
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Careful with aggressive «optimisers». Options like combining and minifying all the CSS and JavaScript, or deferring everything, buy tenths of a second and break menus, forms and carts with impressive ease. Turn one on at a time and use the site properly after each — including buying something, if you sell. If something breaks, common WordPress errors.
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