PrestaShop slow: what you fix yourself, what the host and a developer fix
When PrestaShop is slow, work out what is slow: the whole store, certain pages or only the admin. Then check three settings in Advanced Parameters > Performance: debug mode, the cache and template compilation. If they are fine and the first server response still takes long, it is a job for your host. Heavy modules and the theme are work for you or a developer.
Author: The TellMyShop team. A guide for PrestaShop store owners: the cause, the manual fix and the same work in a chat conversation.
Last updated: · 5 min read
What exactly is slow?
The answer decides who fixes the problem. A slow store and a slow admin are often two different problems.
Measure three types of page: the home page, a category with many products and a product page. Use PageSpeed Insights and note the results for mobile and desktop. The report shows two things worth telling apart. The first is the server's first response time, meaning how long the store thinks before it sends anything. The second is everything that happens afterwards in the browser: images, scripts, fonts. What each metric means is explained by web.dev in its guide to Core Web Vitals.
A long first response points to the server, PrestaShop settings or modules. A fast response with slow rendering points to images, the theme and third-party scripts.
Why did the store suddenly slow down when it used to be fine?
Because something changed, and a sudden slowdown almost always has one cause. Before you start optimising everything at once, think back over the last few days.
- A new module or a module update, especially one with elements on every page.
- Developer work that left debug mode on or forced template compilation.
- A PHP version change, or your host moving the store to another server.
- An import of a large number of products or images.
- More traffic, including bots crawling thousands of filter combinations in categories.
The last point is easy to miss. Google explains how to limit crawling of such addresses in its guide to faceted navigation. When you find the change, reverse it as a test and measure the same pages again.
Who fixes what: you, the host or a developer?
Each cause has its owner. This table saves you an email exchange where everyone passes the problem on.
| Symptom or cause | Who | What to do |
|---|---|---|
| Debug mode on | you | turn it off in Advanced Parameters > Performance |
| Cache off or forced template compilation | you | turn the cache on, set compilation to “Recompile templates if the files have been updated” |
| Unneeded modules with scripts on pages | you | disable as a test, compare the measurement |
| Heavy product and banner images | you | shrink files before uploading, check the WebP format |
| Long first server response despite good settings | host | a stronger plan, current PHP, server-side PHP cache |
| Old PHP version | host | change the version in line with the PrestaShop requirements |
| Bloated database, slow admin | host or developer | clean statistics data and old carts, with a backup |
| Heavy theme, slow filter module, custom code | developer | measurement, code optimisation, a different theme or module |
A wider list of causes is described by Astrabit (in Polish). HelpGuru shows database cleanup step by step (also in Polish). Only ever do it with a backup.
Which settings can you check yourself in fifteen minutes?
They are all on one admin page: Advanced Parameters > Performance. The PrestaShop documentation describes it.
- Debug mode: off. When it is on, part of the cache is disabled and every page is slower. It is often left on after developer work.
- Template compilation: not forced. Forced compilation only makes sense while someone is working on the theme.
- Template cache: on.
- Combining and compressing CSS and JS files: on. After turning it on, check that the pages look right. If something breaks, turn the option off and report it to the theme author.
- Clear the cache and measure the same three pages again.
Write down the results before and after. Without a measurement you will not know which change helped.
How the chat helps, and what it won't do
Your chat (Claude or ChatGPT) diagnoses and tidies up the store. It will not replace better hosting, measure page load times or optimise theme code. In TellMyShop Free it runs a technical review of the store. It checks debug mode, the template cache and file combining. It also reads errors from the log for the last 7 days and the list of modules.
You: The store has been slow for a week, and so has the admin. Check what could be causing it.
Your chat: Technical review:
Debug mode is on. This is the most likely cause, because it disables part of the cache. You can turn it off in Advanced Parameters > Performance.
Combining CSS and JS files is off.
The log for the last 7 days has 230 warnings from the visitor counter module, on every page.
4 pop-up modules are installed, 3 of them active on the home page.
If the first server response is still long after these changes, ask your host about the PHP version and the PHP cache.
Tidying up modules needs TellMyShop Pro and the Modules switch turned on in the module panel. The switch works for 24 hours and needs a database backup made the same day. Then the chat can disable unneeded modules as a test and change their settings, for example the number of products in a home page block. You see every change in a preview before it is saved. See the use cases reviewing and changing module settings and safely removing an unused module.
You can start the review in TellMyShop Free. How to choose modules to disable is covered in the post on unneeded PrestaShop modules. Where to find error messages is explained in the post on PrestaShop debug mode.
Questions and answers
Where do I start when my PrestaShop store is slow?
With a measurement and one page at a time. Check the home page, a category and a product page in PageSpeed Insights. Then open Advanced Parameters > Performance and make sure debug mode is off and the cache is on. These two settings most often explain a sudden slowdown after work on the store.
Why is the PrestaShop admin slower than the store?
The admin does not use the same cache as the storefront and runs more database queries. Statistics modules on the dashboard and bloated visitor data tables slow it down too. It helps to turn off unneeded dashboard blocks, clean up statistics data and get a stronger database server, which is a job for your host.
Will changing hosting speed up PrestaShop?
Often yes, when the measurement shows a long server response time and the store settings are correct. A weak server, an old PHP version or no server-side PHP cache slow down every page. Before you switch hosts, ask your current one about these three things. Sometimes a higher plan is enough.
Will disabling modules speed up the store?
Only if you disable the ones that add work on customer pages: scripts, pop-ups, chat widgets, counters, heavy blocks on the home page. Modules that only work in the admin barely change store speed. Disable each module as a test first and compare the measurement before and after.
Will the chat speed up my store?
It will not replace a better server and it does not measure page load times. The chat runs a technical review of the store, points to settings and modules worth checking and helps tidy up modules. The review works in the free TellMyShop Free. Disabling modules and changing their settings need TellMyShop Pro and the Modules switch.
PrestaShop is a registered trademark of PrestaShop SA. Claude is a trademark of Anthropic PBC. ChatGPT and OpenAI are trademarks of OpenAI. TellMyShop is not affiliated with these companies.