---
title: Forms 4 - Breaking changes
slug: cms-12/docs/forms-4-breaking-changes
docTags: 
createdAt: 2026-08-10T15:55:56.000Z
---

:::hint{type="info"}
**Note**
[Optimizely Forms](docId:3SbSlJZIS_3iFmghfQA3J) is supported by MVC-based websites only.
:::

## EPiServer.Form.Core

This release implements a feature request to support the validation of multiple elements at once.

- When a visitor clicks **Submit** and has JavaScript enabled, elements are validated at once (except CAPTCHA because it needs server-side validation).
- In non-JS mode, elements are validated at once. New behaviors in this release:
  - Validation messages displayed on each failed element
  - Input data on the forms is not cleared
- On server side, this function:

```javascript
  EPiServer.Forms.EditView.Internal.ValidationService.ValidateFormData()
```

Processes elements at once, and returns the array of `ValidationInfo`.

## Breaking changes in Forms 4.0

Interface `IValidationService`:

- `ValidateFormData(NameValueCollection formData, out ValidationInfo validationFailInfo)` is marked with \[Obsolete].
- Add `ValidateFormData(NameValueCollection formData, out IEnumerable<ValidationInfo> validationFailInfo)`.