isit the checkout page, the phone field is optional, how to make it mandatory?
Are you using a theme that supports the checkout block? With a block-based theme you can make the mobile phone field mandatory by editing the checkout block, however, if you’re not using a block based theme, you’ll need the help of custom code.
To make the phone field required when using the checkout block, please head over to Pages > Checkout. Then, click on the icon with three horizontal lines on the top left, this will show the list view. There, select the Shipping/Billing address (if you want it to be required on both, in case they are different, you need to do this on both).
If the right sidebar is not showing, please click on the settings icon on the top right. Here’s a screenshot: https://snipboard.io/3uZK27.jpg
On the sidebar, go to the address fields section and make sure the “require phone number” option is checked.
Don’t forget to save the changes.
Here’s a screenshot:
Also, how to change the placeholder from Phone to Mobile?
I recommend using a translation plugin like Say What? Plugin to change or replace the strings in your checkout page. You can read more on that from our detailed guide here.