TL;DR - A page can load slowly because of an issue with Shopify or with the merchant's internet quality. You can use Chrome's built in developer tools or tools like Pingdom to determine the source.

When a merchant's page is loading slowly, the first thing to confirm is whether it's an issue with the page or something local to the merchant like their internet quality. Quick and easy way to check this is to load the page up yourself. If it loads fine, it's very likely an issue local to the merchant.

You can take it a step further though by testing out the speed using a tool like Pingdom http://tools.pingdom.com/fpt/. This will check the page speed and how it measures up to other pages, as well as show the different assets on the page to give you an idea of what might be slowing down the page's load time.

You can also use Chrome's built in developer tools to find slowly loading resources. We have an Intro to Chrome Developer Tools Guru card on how to use them.

Pingdom and other 3rd party testing services can be sent to the merchant so they can try it out in the future, but set the expectation that we will not troubleshoot those tools as they are built by other companies.

Determining The Source

Once you've checked the page's speed and determined it is loading slowly or not responding well, you can try and figure out what the cause is.

A tool like Pingdom http://tools.pingdom.com/fpt/ might point you in the right direction as to what's causing the slow load time, but it can sometimes be difficult to tell.

A whole bunch of images.

For pages with a ton of images attempting to load, that's a good place to start. A lot of images, especially high quality images, will tend to load more slowly.

Let the merchant know they can try to reduce their images' size or choose to display fewer images. We set the limit for image pagination at 50, but this doesn't mean it's the optimal number of images to use.

We have a public doc with recommended image sizes.

A whole bunch of apps.

Apps can be super handy for merchants and often don't even make an impact on the storefront. However, some apps are designed to load extra assets to the storefront like livechat modals or image slideshows. These add to the amount of information being loaded on a page. As with images, this is fine in moderation but if there are too many it can have an impact.

Take a look at the merchant's apps and see how many of them might be loaded on the storefront. If you need more than a few fingers to count them, they could be causing speed issues. To resolve the merchant can look at removing one or two of these apps. Overall this is probably better for their business, it can be pretty annoying to be pestered with all sorts of popups and modals.

Unresponsive Script

This behaviour tends to manifest as the site hanging out as a blank page and doing nothing for an extended period, then everything loading all at once. To determine the culprit, Chrome Developer Tools are the best tool. Open a new Incognito window, activate the Tools in Network mode, ensure that Record is on, and then visit the merchant's page. For a busy but functioning page, the timeline will look something like this:

The events being run are all pretty normal. This is a more stock Shopify storefront:

And here's a website with a sickness:

Clicking through on the script in question will give you some clues as to what app or code is implementing it, who it's trying to contact, and if we're fortunate why it's taking so long.