In short
Google retired its own Mobile-Friendly Test and the Mobile Usability report on 1 December 2023 and has pointed to Lighthouse since then. The question whether a website works well on phones has remained. This test opens your home page in a real browser with phone dimensions, shows you a screenshot and checks the most important points.
Why the phone view matters so much
Since switching to mobile-first indexing, Google assesses websites by their mobile version. In June 2024 Google announced that after 5 July 2024 it would crawl even the last remaining websites with the smartphone Googlebot only. If your site is hard to read on a phone or content is missing, that is exactly the version Google counts. And for your customers it counts anyway: anyone looking for a tradesperson or a hairdresser on the go searches on their phone.
What the test checks
| Check | Threshold | Why |
|---|---|---|
| Set up for phones | width=device-width in the viewport | Without it the page is shown like on a computer and scaled down tiny |
| No sideways swiping | page not wider than the screen | Otherwise content is cut off |
| Readable text | text at least 12 pixels | Same threshold as Lighthouse for legible font sizes |
| Tappable buttons and links | at least 24 × 24 pixels | Minimum size under WCAG 2.2, criterion 2.5.8, links within text exempt |
| Encrypted connection | https | Without it browsers show a warning |
| Load time | good under 3 seconds | Measured from my server, an approximation |
| Data size | good under 2 MB | Large pages cost time and mobile data |
The thresholds for load time and data size are rules of thumb, not Google requirements.
How to test your website on a phone
- Enter your home page address and start the test.
- Look at the screenshot: is the phone number visible? Is it clear right away what you offer?
- Read the points under problems and notes.
- Also open your site on your own phone and tap through the menu, contact form and phone number once.
For a deeper check, Google recommends Lighthouse, built into Chrome (F12 key, "Lighthouse" tab), or PageSpeed Insights at pagespeed.web.dev.
What to do if the test finds problems
- Viewport missing: the site is not built for phones. A small change rarely fixes that, usually it needs a new responsive design. What that means is explained in Responsive web design.
- Sideways swiping: usually images, tables or embedded content that are too wide. The example in the result shows which element is too wide.
- Small text or small buttons: adjust font sizes and spacing in the design.
- Slow page: make images smaller, remove unnecessary scripts. More in Improve website load time.
I design my own sites for phones first and check them on real screen sizes before they go live.
Frequently asked questions
Does Google's Mobile-Friendly Test still exist?
No. Google retired the test and the Mobile Usability report on 1 December 2023 and recommends Lighthouse instead.
Is the test free?
Yes, without sign-up. To avoid overloading the server, the number of tests per person is limited.
Why does my site look different in the test than on my phone?
The test uses a browser 390 pixels wide, like many current phones. Other devices, a saved cookie banner choice or content that only loads after scrolling can cause differences.
What happens to my website during the test?
My server requests the home page once, like a normal visitor. Neither the address nor the screenshot is stored.
Sources
- Google, retirement of the Mobile-Friendly Test: developers.google.com/search/blog/2016/05/a-new-mobile-friendly-testing-tool
- Google, mobile indexing announcement (June 2024): developers.google.com/search/blog/2024/06/mobile-indexing-vlast-final-final.doc
- W3C, WCAG 2.2, criterion 2.5.8 Target Size (Minimum): www.w3.org/WAI/WCAG22/Understanding/target-size-minimum.html
- Lighthouse, legible font sizes: developer.chrome.com/docs/lighthouse/seo/font-size
As of 5 November 2026.