# Conditional Logic in Forms, With Examples > What conditional logic in a form is, the six things a logic rule can do, and worked examples: follow-up questions, skipped pages, early endings and totals. By Uyi Abraham (Founder and CEO, Vonza). Published 2026-11-07, updated 2026-11-07. Category: Marketing and sales. 4 min read. Canonical: https://vonza.net/blog/conditional-logic-forms 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](https://vonza.net/blog/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](https://vonza.net/blog/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](https://vonza.net/blog/how-to-make-a-scored-quiz). For everything else, see [Vonza Forms](https://vonza.net/forms) or start from a [form template](https://vonza.net/form-templates). ## Frequently asked questions ### What is conditional logic in a form? Conditional logic changes a form based on the answers someone gives. It can show or hide a question, make it required, skip a page, end the form early or work out a value, so each person only sees what applies to them. ### Can logic send people back to an earlier page? No. In Vonza Forms, Skip to page only goes forward, to a later page. That keeps the form from looping. To repeat a set of questions, such as one per guest, use a repeating group block instead. ### Can a form react to the link someone used? Yes. A logic rule can test a parameter in the form's link, and a hidden field can be filled from the link. So a link with ?plan=premium can skip the questions premium customers have already answered.