Parsing user agent - creating dynamic form

Questions / Help
1

I would like to use a different layout and template depending if the user uses PC or a smartphone.
So, I would like to switch layout and template by checking user agent.
What is the best way to check user agent and switch layout and template without using library?

I was thinking having a list and then filtering it for Mobile user agents… but seems hacky and bad practice.

2

Where there is no other choice I have used the Device Atlas database. But your concerns are reasonable: They have over 21,000 agent strings in their database!

I believe it is vastly better to understand the browser capabilities over trying to do user agent detection. The best alternative would be responsive templates. Or as a last resort some small JS to transmit screen dimensions (for example), but the experience is much better for the end user.

3

Also many css frameworks are responsive and adapt layout to media breakpoint.

4

I also believe that CSS can handle most of your intentions, but you can enhance with: ua_parser or us_inspector. Maybe even cache most common.