When is it appropriate to change a site's tabindex?

Question

I'm building a sign-up form filled with multiple input fields. To increase the rate in which the form is filled out I decided to dynamically set the tabindex at the first input field. Naturally after tabbing through the collection of input fields it defaults to the beginning of the DOM and continue down and around the form.

My question I guess you can say is split into two parts. The first being, should the tab index reset after the fields are tabbed through or continue straight down the DOM from the form? The second as stated in the title, when is it usually appropriate to change a site's tabindex?

Answer 1

Personally, I think messing with tabindex is messy business. It's difficult (if not impossible) to use it in a way that is intuitive for users. If I (and I think most other people on the web) see a form element I need to interact with, I click on it and tab from there rather than trying to tab to it up front.

Two possible use-cases for tabindex that I have run into are:

1. You have elements which may appear in a different order responsively without moving in the markup, causing the tab order to appear incorrect.
2. You need to take something out of the tab order.

If you want to accelerate the process of filling out forms, a noble goal, I would suggest focusing the first form element when the user hits the page. This allows them to get right into it and tab order will proceed as normal from there. It also has the bonus of being a clear visual cue.