# Conditional logic

Show, hide, require, and jump to pages based on answers, or calculate values and stop a submission. Write a rule, combine conditions, and test it in Preview.

## What logic can do

A logic block holds one or more rules. Each rule reads **When** these conditions are true, **Do** these actions.

| Action | What it does |
| - | - |
| Show / Hide | Shows or hides any block: a question, a paragraph, an image, or one option of a choice question. |
| Make required / Make optional | Requires a question on some paths only, or relaxes it on others. |
| Set next page | Skips to a page, so different answers lead down different paths. |
| Calculate value | Works out a total, score, or price in a [calculated field](https://formstep.io/docs/building-forms/calculated-fields/). |
| Set payment amount | Sets, raises, or lowers the price of a [Payment question](https://formstep.io/docs/building-forms/payment-collection/#dynamic-pricing). |
| Prevent navigation to next page | Stops the respondent from going on, with an optional message saying why. |
| Prevent form submission | Stops submission until conditions are met, such as terms accepted, with an optional message saying why. |

## Add a logic block

A logic block sits on the canvas between questions, like any other block.

1. **Add a Logic block**

   Click **Logic** in the Blocks tab, or type `/logic` on the canvas.

2. **Set the conditions**

   Pick a question, an operator, and a value. **Add condition** adds another row.

3. **Choose actions**

   Pick an action, such as Show or Set next page, and what it acts on: a question, block, option, or page.

4. **Add more rules (optional)**

   One logic block can hold several rules, each with its own conditions and actions.

To show a block only sometimes, hide it with **Hide** in its block menu, then add a rule that shows it.

The **Logic** tab of the side panel lists every rule in plain words, such as _When Plan is Pro, show VAT number_. Click a rule to jump to it. **Needs attention** shows rules that point at a deleted question.

## Conditions

A condition can read questions, hidden fields, calculated fields, and the respondent's language. With two or more conditions, click the **And** or **Or** pill to switch: with **And** all must be true, with **Or** one is enough.

**Add a set of conditions** adds a group with its own And/Or, for rules like “plan is Pro _and_ (country is Norway _or_ Sweden)”. A set cannot hold another set.

![A logic block whose When section joins Plan is Pro and a set headed Any of these, holding Country is Norway and Country is Sweden, with an And pill on the outer bracket and an Or pill inside the set, and a Do action that shows the VAT number question.](https://formstep.io/docs/images/building-forms/logic-block.png)

Plan is Pro and (country is Norway or Sweden): an And rule with an Or set inside.

### Operators

The operators depend on the question. The main ones are below; most also have an opposite, such as **is not empty**. Text comparisons ignore capital letters and spaces at either end.

- Text, email, web address, and phone: is, is not, contains, starts with, ends with, is empty.

- Numbers, ratings, and scales: is, is greater than, is less than (or equal to), is between, is empty.

- Dates and times: is, is before, is after, is between.

- Radio Buttons and Dropdown: is, is not. Checkboxes and picture choice: has checked any of, all of, or exactly.

- Others: Toggle Switch is on or off, Signature is signed, File Upload has file, Payment is completed, Ranking option is ranked first, Matrix row answer is.

Logic can show or hide **Schedule appointment** and **Documents**, but cannot read them. See [Cal.com scheduling with logic](https://formstep.io/docs/integrations/cal-com/#logic).

> **A hidden question has no value**
>
> When logic hides a question, its answer is ignored in conditions, calculations, and the payment amount, and is not saved. The same goes for questions on a skipped page. A hidden question is never required. Hidden _fields_ always keep their value.

## When rules disagree

When two matching rules disagree, for example one shows a block and another hides it, the first rule in the form wins, and the editor flags the rule that never applies. To show a block for several answers, one rule with conditions joined by **Or** is easier to read than several rules.

## Common patterns

### Show a follow-up question

After a 1 to 5 Star Rating, a rule says: when rating **is less than or equal to** 3, **Show** “What could we improve?”.

### Branch to different pages

An event registration form asks: “Are you attending in person or remotely?” Three rules follow:

- When attendance **is** “In person”, **Set next page** “Venue details”.

- When attendance **is** “Remote”, **Set next page** “Streaming setup”.

- When arrival time **is not empty**, **Set next page** “Confirmation”. Arrival time is a required question on “Venue details”.

A jump happens when the respondent clicks Next on the page with the question it reads. The third rule lets in-person attendees skip “Streaming setup”, so both paths end on “Confirmation”.

### Calculate a score and branch on it

Three Star Ratings add up into a calculated field, “Lead score”, with **Calculate value**. A second rule: when Lead score **is greater than** 12, **Set next page** “Priority follow-up”.

### Stop submission below a total

When Order total **is less than** 10, **Prevent form submission**. Type the reason in **Message shown to respondent**, such as “Your order must total at least 10”, so they know what to change.

> **Test logic with Preview**
>
> **Preview** runs your logic. Fill in the form there to check every branch before you publish.

## Next steps

[Calculated fields](https://formstep.io/docs/building-forms/calculated-fields/) — Work out a total, score or price

[Form structure](https://formstep.io/docs/building-forms/form-structure/) — Split a form into pages to jump between