What are the first thing you check when a shopify store feels slow , especially on mobile?
Hey @Mia-Hazel ,
I usually start by checking the store on my phone to see where it actually feels slow. Then I check pagespeed Insights to see if the issue is coming from large images, apps/scripts, or heavy theme code.
In my experience third party apps and unoptimized images are often the first things worth checking on mobile.
Thank You!
First thing I check is not the score. A Shopify store sitting between 30 and 50 in Lighthouse is normal, and chasing that number wastes days.
Open PageSpeed Insights and read the field data at the top instead, the part from real Chrome users. If that section says your LCP is fine, the store is not slow for actual visitors, whatever the lab score says. If there is no field data, the store has too little traffic and you are back to judging by hand on a real phone.
Then three things, in this order:
- What the LCP element actually is. Usually the hero image. If it is a 2 MB PNG served at full width, nothing else you do matters.
- How many third party scripts still load. Open the network tab and count the domains that are not yours. I looked at a store this morning that was shipping 273 scripts on the homepage, and the owner thought his problem was traffic.
- Leftover code from apps you removed. Uninstalling does not always clean the theme, so search your theme files for the app name. Dead script tags from apps a merchant no longer pays for are common and cost nothing to remove.
Hi @Mia-Hazel
Welcome to the community.
What is a store link? One that feels slow on mobile; maybe we can help with specific issue.
Usually I check the apps and third party scripts first. A store can feel fine on desktop and then become painfully slow on mobile because a bunch of apps are loading scripts that aren’t really needed on the first screen.
Then I look at the images, especially the hero image and anything above the fold. Huge uncompressed images are still one of the easiest ways to make a mobile store feel slow.
After that I’d check the theme itself and look for unnecessary sections, animations, popups and custom JavaScript. I also run the store through SiteGuru because it can flag some of the technical and performance related issues that are easy to miss when you’re just browsing the site yourself.
I’d test an actual product page too, not just the homepage. Sometimes the homepage is fine but the product page has reviews, recommendations, chat widgets and tracking scripts all loading at once.
Basically I’d find out what’s actually taking the time before removing things. Otherwise it’s really easy to spend hours “optimizing” something that wasn’t the problem.
Hi @Mia-Hazel , there are a few essential things you can go through when thinking of checking speed on mobile
- The first thing LCP: check your hero image first, then slideshow and then product image, optimize them for mobile loading, compressed efficiently can help with speed while maintaining good display on mobile
- Then go through all images thoroughly, this can be the main killer with oversized PNGs
- Next thing you can check is any app/script bloat, make sure you only keep really neccessary ones, don’t let too many apps that load storewide slow down your site while they can only solve a small friction
- Optimize your homepage, don’t try to stuff too many modules, focus on having a clear and effective hero
Okay so now you can try going through the above mentioned bullets
- Run PageSpeed Insights and Shopify theme speed report
- Monitor LCP element and largest resources
- Compress or resize images
- Remove non-critical apps
You can totally handle all these step by step on your own, but if you’re looking for some help to save time and have these handled effectively, you can try some tools such as SEOWILL, which can help with one-click site speed-up (applies safely on a duplicated theme, so your original stays intact), image optimization/compression with restore options
That combo is useful when the store “feels fine” on desktop but crawls on mobile — usually images + extra scripts.
Hi @Mia-Hazel
I am actually still learning about these things myself, but based on what I’ve learned so far,I’d say the first thing I check is the mobile PageSpeed.Then I Look for large or unoptimized images, heavy apps/scripts, unused javascript/CSS, and third-party tracking codes.
I also check for auto playing MP background videos or heavy GIFs above the fold,since they can reall slow down mobile loading and use a lot of data.
Another thing I’ve learned is that uninstalling an app does not always remove all of its code. Somethimes leftover scripts in theme.liquid or asset files can still make network request and affect performance.
Finally, I check LCP and other core web vitals to understand whats actually causing the slowdown.
I hope this helps!
I’d start with the mobile homepage in Chrome DevTools and look at what’s actually blocking first paint.
A lot of slow stores have one big hero image, a heavy app embed, or a font file that’s loading before the page can show anything useful. So I’d compare the homepage, a collection page, and a product page because the bottleneck is often only on one of those.
If you want a quick way to narrow it down, open the page in an incognito window on your phone, then turn off one app at a time in Shopify and reload after each change. That usually tells you fast whether it’s the theme, an app, or just oversized media.
What feels slow on mobile for you, the homepage load, scrolling, or tapping into a product?
Hello @Mia-Hazel, Bristan_FARRE’s field-data-first approach above is the right instinct, chasing the Lighthouse number itself wastes time. One thing specific to “fine on desktop, slow on mobile” that’s worth checking: some themes conditionally load extra JS only under the mobile breakpoint, like a mobile nav drawer or a sticky add-to-cart bar, so that script never runs on desktop and won’t show up if you only test there. Open the network tab specifically in mobile emulation to catch anything like that. Thanks
One thing the answers above have not covered, and it explains a good share of the I-removed-apps-and-it-is-still-slow cases: apps you uninstalled months ago can still be loading. Uninstalling removes the app’s access, not what it wrote into theme.liquid or the snippets folder while it had access. Older apps installed through the theme Asset API, and those script tags stay behind, still requesting a file from a domain that may not even answer anymore. A request that times out looks harmless in a lab score but shows up as a long wait on a real phone.
Quick check without any tool: open the Network tab on a product page, sort by domain, and list every third-party host. Match each one against the apps actually installed in your admin. Any host with no matching app is a leftover, and the fix is deleting the tag from theme.liquid, not adding another optimizer app on top. I wrote up the manual version here: Store slower after uninstalling apps? How to check for leftover app code in your theme (and remove it safely). For disclosure, I build a small app that automates that scan (Upright Cleaner), which is how I know how common it is.
Hi, @Mia-Hazel
When a store feels slow, especially on mobile, I usually don’t start by changing everything at once. I try to identify where the delay is coming from first, because it’s often a theme, app, image, or third-party script causing most of the slowdown.
Check the homepage first
I’d run the store through PageSpeed Insights and look at the mobile results, especially the LCP element. If the hero image, banner, video, or another large above-the-fold element is taking too long to load, I’d start there.
Review the Shopify apps
I’d check which apps are adding scripts to the storefront, especially reviews, chat, upsells, tracking, and popups. If you have unused apps, remove them, as their scripts can still add unnecessary load on mobile.
Check the theme
I’d look through the theme for unnecessary animations, sliders, custom scripts, popups, and sections that are loading on every page. A store can have a well-built theme but still become slow after adding lots of extra functionality over time.
Review images
I’d check the hero and other large images first to make sure they’re properly sized and compressed. For images below the fold, use lazy loading, but make sure the main LCP image loads quickly.
Test product and collection pages
I’d also test a product page and collection page separately from the homepage. If those pages are much slower, I’d look at product galleries, reviews, recommendation widgets, and apps that only load on those templates.
Once those areas are checked, you usually have a much better idea of what’s actually slowing the store down instead of just chasing the PageSpeed score.
If performance is still an issue after the usual theme and app cleanup, tools like Website Speedy can also help with image optimization and frontend performance improvements, but it’s completely optional to use.
Disclaimer: I’m affiliated with Website Speedy.