Required or optional fields: how to mark them in a form

On a landing page form, every field silently asks the visitor a question: “do I really have to fill this in?”. Marking requirements badly produces two symmetrical failures — visitors who abandon a form that looks longer than it is, and submissions rejected for a missing field, with the error message and friction that come with it. The asterisk convention solves part of the problem; it hides another, more important one.

What usability research says

Field marking is one of the twenty recommendations formalized by Javier Bargas-Avila and colleagues in “Simple but Crucial User Interfaces in the World Wide Web: Introducing 20 Guidelines for Usable Web Form Design” (2010), one of the most-cited syntheses on form design: if a form mixes required and optional fields, the marking must be explicit and systematic, and the asterisk is only understood because it has become conventional — not because it is self-evident. A share of users, especially less web-savvy ones, don't know what it means.

The follow-up to that work, “Designing Usable Web Forms: Empirical Evaluation of Web Form Improvement Guidelines” (Seckler, Heinz, Bargas-Avila, Opwis and Tuch, CHI 2014), tested those recommendations empirically on real forms: the guideline-compliant versions produced faster completion, fewer errors and higher satisfaction. In other words, these details — marking, field order, label position — are not a matter of taste: they are measurable.

Rule #1: shrink the problem before signalling it

The best way to mark optional fields is to have no optional fields. An optional field is an admission: the information is useful enough to ask for, not useful enough to require. On a landing page — where every extra field costs conversions, as our article on the ideal number of fields shows — that trade-off almost always resolves the same way: remove the field, or make it required if it genuinely conditions how the request is handled. “Bonus” information can be collected later, once the relationship has started, by email or during the first conversation.

Three marking strategies, in order of preference

1. All required: mark nothing, say it once

If every field is required — the ideal case for a short form — marking each one individually only adds visual noise. A single line at the top (“all fields are required”) is enough, and the form looks cleaner for it. That's the configuration of forms stripped to the essentials: first name, email, and at most the one qualification field that truly matters.

2. Mixed: mark the optional, not the required

If one optional field must stay, an explicit “(optional)” next to its label is clearer than asterisks on all the others: it marks the exception rather than the rule, needs no legend, and lightens the form whenever required fields are the majority — which should always be the case on a landing page. This preference for the explicit word over the symbol echoes what we detail in our article on form microcopy.

3. The asterisk: acceptable, if you're rigorous

The asterisk remains defensible on long quote or registration forms, where the convention is well established. Three conditions: the legend (“* required field”) must be visible before the first field, the symbol must sit next to the label (not floating at the end of the line), and it must be backed by accessible marking for screen readers (the required and aria-required attributes), a point developed in our guide to landing page accessibility.

The mistakes that cost submissions

• Marking both required and optional fields — doubling asterisks and “optional” labels forces the visitor to decode two systems; pick one.
• Revealing the requirement at submission — a required field discovered through an error message after clicking is the worst kind of friction; the requirement must be visible before typing.
• Relying on color alone — a red label is neither universally understood nor perceived by colorblind users; marking must go through text or symbol, never color only.
• Putting the asterisk legend at the bottom of the form — it must precede the fields, where the visitor needs it.
• Forgetting the GDPR case — the optional consent checkbox (newsletter) must be clearly separate from the consent necessary to process the request, as required by the compliance rules detailed in our article on GDPR and forms.

On a landing page, the question barely arises

Everything above applies to forms in general. On a lead-capture landing page, the practical conclusion is more radical: a form of 2 to 4 fields, all required, with no asterisk or label, and one introductory sentence if needed. That's how LanderKit templates are built — from the discovery-call form of the Coach & Consultant template to the two-step estimate of the Real Estate template, which moves optional questions to a second step instead of cluttering the first, following the multi-step form pattern. For the full picture — placement, labels, validation, button — see our complete landing page form guide.