Html5 Email input pattern attribute

Giving feedback to users

Enfolding user experience and minimizing errors call for clear communication. When the input does not match the pattern, users should get an intelligible message that guides them towards rectification. Here, the title attribute is your friend, describing the format expected. To jazz that up and provide real-time feedback, bring in some JavaScript goodness.

<!-- Be polite, say please :) -->
<input type="email" pattern="^\S+@\S+\.\S+$" 
       title="We need it like this: [email protected]" 
       oninvalid="this.setCustomValidity('Whoops! That doesn't look like an email address.')"
       onchange="this.setCustomValidity('')">


Dealing with diverse email formats

Though the fast answer regex might get you started, the reality of email formats is like the variety of dog breeds: vast and assorted:

• Special characters in usernames: Include these misfits in the username part of the regex (^[a-zA-Z0-9._%+-]+)
• Hyphenated domain names: Allow hyphen-riddled domains in the domain portion of the regex ([a-zA-Z0-9.-]+)
• TLD length flexibility: Make sure top-level domains of various lengths are catered for (.+\.[a-zA-Z]{2,}$)

Don't be falsely lulled into complacency by the built-in HTML5 email input type validation, for they don’t ward off every complexity of email formatting, like:

• Vintage formats: Not widely used, but still valid according to the spec (e.g., "user@[IPv6:2001:db8::1]")
• Foreign characters: Email addresses dipped in non-ASCII sauce (needs punycode conversion)

Deep dives for robust validation

Turns out email validation has more layers than an onion. Here are few more strategies to ensure you've covered all bases:

Server-Side Validation

Safety first, so leverage server-side validation as your failsafe checkpoint. This stalwart line of defense against invalid data becomes essential since client-side validation could be skipped like a queue.

Go Old School

Use Modernizr to make a feature support check and enact polyfills for vintage browsers. This ensures your forms manage a consistent experience across the clientele.

Harness Framework Attributes

Working with a front end framework? Use that gift! Frameworks like Angular offer built-in validation mechanisms, e.g., ngModel, lending to simpler validation processes and more maintainable code.

Spice up Your Client-Side Game

Leverage Ajax and JSON to perform real-time checks on user's data before submission, providing a more intuitive user experience and preemptively catching errors.

Test, Then Test Some More

Online tools like RegExr can be your playground to test your regex patterns in varied scenarios. Verify your optimized regex pattern against a diverse range of email addresses.