This article is not about why website speed or performance is important.  I am assuming you already know its importance. This is about why we need to test website performance on different device types.

Four main reasons why we need to do that :

1. Website Content is different
2. Internet connection type is different
3. Javascript execution and browser performance is different
4. Most of your users come from different devices

Website Content is different

Mobile users do not need all the content like desktop users because their intent is different from desktop and laptop users. Many websites design differently depending on device type.
Not only look and feel of the website, even content is different depending on the device. For example, displays different content on desktop, tabs and mobiles.

You can check performance on different devices at is taking 1.52 sec on Laptop, 1.17 sec on Samsung Tab 2, 0.97 sec on iPhone 7 .

You can see how the website look and content is different on three different device types.



When the website content is different i.e text, CSS, images, javascript etc… then website speed also changes accordingly.

Internet connection type is different

On average we know that most of the desktop and laptop users use home or office wifi but mobile and tablet users use 4G LTE or 4G at present. Depending on internet connection type, latency & bandwidth changes. So even if the content is same, website speed changes because of the above factors.

For example, to download 200 KB resource it takes 0.032 sec with WIFI (50 Mbps, 30 milliseconds latency), 0.106 seconds on 4G LTE (15 Mbps, 70 milliseconds latency ) and 0.178 seconds on 4G ( 9 Mbps, 170 milliseconds latency ).


Javascript execution and browser performance is different

Normally desktops and laptops are more powerful comparing to tablets and mobiles.  When the browser gets required resources from the server,  powerful devices always execute and render them faster comparing to less powerful devices. Even when the content is same, their execution and rendering time changes.

You can see in the below graph how exeuction time changes as processor & ram configurations change.


Most of our users come from different devices

We all know that our users won’t come from just one device type. Normally on average, every person will have minimum 2 devices (one laptop and one mobile ). Most probably he or she will use laptop at home or office and mobile everywhere else.

Most website owners will check their website speed on desktop and don’t bother about other devices. Sometimes they may even guess their website speed on other devices depending on how it is performing on desktop using some mathematical formulas . This is not good.

If you want to make your website users happy who are browsing the website using different device types, it’s always better to test website speed on different device types not just on a single device. 

You can check your website speed on all devices for free at



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