Conditional Logic in Forms, With Examples

Conditional logic is a set of rules that change a form based on the answers someone gives. Instead of one long list of questions for everyone, the form shows a follow-up only when it applies, skips pages that do not, and ends in the right place. This guide explains what a rule can do in Vonza Forms, with examples you can copy.

How a logic rule works

Every rule has the same shape: when something is true, then do something, and optionally otherwise do something else.

The "when" part tests answers, using checks such as equals, contains, greater than, between, before or after a date, is empty, or how many options were picked. A rule can combine several checks and match when all of them, any of them or none of them are true. Besides answers, a rule can test a score, a running total, a variable you set, or a parameter in the form's link.

The six things a rule can do

• Show, hide, require or make optional: show a question only when it applies, or make a question required only for some people. A question can be set to "Hide until logic shows it".
• Skip to page: go straight to a later page, passing the ones that do not apply.
• End the form: finish early on a thank-you screen. A form can have up to 10 thank-you screens, so different answers can end in different places.
• Set a value: fill in a question or a hidden field, for example a lead type or a team name.
• Calculate: change a variable with a formula, using + − × ÷ and round(), min(), max(), if(), sum() and count().
• Recall: not a rule, but it works with them. Earlier answers, link parameters and scores can appear in later questions, descriptions and the thank-you screen.

Example 1: a follow-up question for "Other"

A contact form asks "How did you hear about us?" with five options and "Other".

• When "How did you hear about us?" equals "Other", then show "Where did you hear about us?".

Everyone else never sees the extra question. Set the follow-up to "Hide until logic shows it" so it starts hidden.

Example 2: require a detail only when it matters

A registration form asks "Do you have any allergies?" with Yes and No.

• When the answer equals "Yes", then show "Please list your allergies" and require it.

People with no allergies move on; people with allergies cannot skip the detail you need.

Example 3: skip a page that does not apply

A client intake form has a page for existing clients and a page for new ones.

• When "Have you worked with us before?" equals "Yes", then skip to the "Your project" page.

New clients see the "About your business" page first; existing clients go past it.

Example 4: end early when someone is not a fit

A coaching application asks about budget on page one.

• When "Monthly budget" is less than your minimum, then end the form on a thank-you screen that suggests a free resource instead.
• Otherwise, continue to the full application.

Nobody fills in three pages only to hear it is not a match, and you only review applications that fit.

Example 5: work out a total

A quote request asks for the number of rooms and the type of cleaning.

• Calculate a variable estimate as rooms × the price per room, plus a fixed amount when "Deep clean" is ticked.
• Show the estimate on the thank-you screen with recall.

For a form that takes the money too, use a payment step with its own prices rather than a calculated total; see take payments with a form.

Example 6: react to the link

You send existing customers a link with ?customer=yes.

• When the link parameter customer equals "yes", then hide the "How did you hear about us?" question.

Pair it with a hidden field set to "Fill from the link" and the value is also saved with each response.

See the whole flow on one map

A form with many rules is easier to check as a picture. The logic map shows every page, each jump as an arc and each early ending as a dashed line, so you can spot a page nobody can reach before you publish. Vonza also checks the form when you publish and flags broken logic before the form goes live.

Keep logic simple

• Write the form without logic first, then add rules only where someone would otherwise see a question that does not apply.
• Prefer one clear rule to several overlapping ones.
• Preview the form and walk through each path before you publish.

Next steps

Logic pairs well with pages; see multi-step forms for when to split a form. Quizzes use the same rules to send people to a result by score: read how to make a scored quiz. For everything else, see Vonza Forms or start from a form template.