---
title: "Validators"
manual: "Form"
version: "main"
permalink: "https://docs.typo3.org/permalink/typo3/cms-form:validators@main"
source: "E/Validators/Index.rst"
rendered: "2026-09-19T16:47:20+00:00"
---

# Validators {#validators}

## Introduction {#validators-introduction}

Validators can be added to all form elements to check user input for "validity" -
i.e. existence, meaningfulness and correctness. For example, you can
determine whether a field has been filled out or if the user has entered a
valid email address. You can also **define** your own **error messages**.
These messages can be edited in the **form editor**.

This chapter **describes** the individual validators and their
**function**.

![In the Inspector - adding validators.](Images/form_validators.png)

## Overview of validators {#validators-overview-of-validators}

### Alphanumeric {#validators-alphanumeric}

This validator checks whether the field contains an alphanumeric string.
"Alphanumeric" means a combination of alphabetic and numeric characters. No
special characters can be entered, only characters from **\[A-Z\] and \[0-9\]**.
The settings of the validator are as follows:

-   **Custom error message**: Custom error message that will be shown if the
    validator fails.

**The validator is available for the following form elements**:

-   ["Text"](https://docs.typo3.org/permalink/typo3/cms-form:form-elements-basic-elements-text@main)
-   ["Textarea"](https://docs.typo3.org/permalink/typo3/cms-form:form-elements-basic-elements-textarea@main)
-   ["Password"](https://docs.typo3.org/permalink/typo3/cms-form:form-elements-basic-elements-password@main)
-   ["Advanced password"](https://docs.typo3.org/permalink/typo3/cms-form:form-elements-advanced-elements-advanced-password@main)

![In the Inspector - Settings of the "Alphanumeric" validator.](Images/form_validators_alphanumeric.png)

### String length {#validators-string-length}

This validator uses *minimum* and *maximum* values to check how many
characters can be **entered**. The settings of the validator are as follows:

-   **Minimum**: Minimum amount of characters the field can contain.
-   **Maximum**: Maximum amount of characters the field can contain.
-   **Custom error message**: Custom error message that will be shown if the
    validator fails.

**The validator is available for the following form elements**:

-   ["Text"](https://docs.typo3.org/permalink/typo3/cms-form:form-elements-basic-elements-text@main)
-   ["Textarea"](https://docs.typo3.org/permalink/typo3/cms-form:form-elements-basic-elements-textarea@main)
-   ["Password"](https://docs.typo3.org/permalink/typo3/cms-form:form-elements-basic-elements-password@main)
-   ["Advanced password"](https://docs.typo3.org/permalink/typo3/cms-form:form-elements-advanced-elements-advanced-password@main)

![In the Inspector - settings of the validator "String length".](Images/form_validators_stringLength.png)

### Email {#validators-email}

This validator checks whether an entered value is a **valid email address**.
International characters and multiple occurrences of the **@ sign**
are allowed by default. The settings of the validator are as follows:

-   **Custom error message**: Custom error message that will be shown if the
    validation fails.

**The validator is available for the following form elements**:

-   ["Text"](https://docs.typo3.org/permalink/typo3/cms-form:form-elements-basic-elements-text@main)
-   ["Email address"](https://docs.typo3.org/permalink/typo3/cms-form:form-elements-special-elements-email@main) (validator is
    automatically active)
-   ["Password"](https://docs.typo3.org/permalink/typo3/cms-form:form-elements-basic-elements-password@main)
-   ["Advanced password"](https://docs.typo3.org/permalink/typo3/cms-form:form-elements-advanced-elements-advanced-password@main)

![In the Inspector - Settings of the 'Email' validator.](Images/form_validators_email.png)

### Integer number {#validators-integer-number}

The validator checks whether an entered value is a **valid integer**. Numbers
with commas are not allowed. The settings of the validator are as
follows:

-   **Custom error message**: Custom error message that will be shown if the
    validation fails.

**The validator is available for the following form elements**:

-   ["Text"](https://docs.typo3.org/permalink/typo3/cms-form:form-elements-basic-elements-text@main)
-   ["Textarea"](https://docs.typo3.org/permalink/typo3/cms-form:form-elements-basic-elements-textarea@main)
-   ["Password"](https://docs.typo3.org/permalink/typo3/cms-form:form-elements-basic-elements-password@main)
-   ["Advanced password"](https://docs.typo3.org/permalink/typo3/cms-form:form-elements-advanced-elements-advanced-password@main)

![In the Inspector - settings of the validator 'Integer number'.](Images/form_validators_integerNumber.png)

### Floating-point number {#validators-floating-point-number}

The validator checks whether an entered value is a **valid floating-point
number**. Only numbers with commas can be entered. The settings of the
validator are as follows:

-   **Custom error message**: Custom error message that will be shown if the
    validation fails.

**The validator is available for the following form elements**:

-   ["Text"](https://docs.typo3.org/permalink/typo3/cms-form:form-elements-basic-elements-text@main)
-   ["Textarea"](https://docs.typo3.org/permalink/typo3/cms-form:form-elements-basic-elements-textarea@main)
-   ["Password"](https://docs.typo3.org/permalink/typo3/cms-form:form-elements-basic-elements-password@main)
-   ["Advanced password"](https://docs.typo3.org/permalink/typo3/cms-form:form-elements-advanced-elements-advanced-password@main)

![In the Inspector - Settings of the 'Floating-point number' validator.](Images/form_validators_floatingPointNumber.png)

### Number {#validators-number}

The validator checks whether the entered value is a **valid number**. Numbers with
commas are not allowed. The settings of the validator are as
follows:

-   **Custom error message**: Custom error message that will be shown if the
    validation fails.

**The validator is available for the following form elements**:

-   ["Number"](https://docs.typo3.org/permalink/typo3/cms-form:form-elements-special-elements-number@main) (validator is
    automatically active)

![In the Inspector - Settings of the 'Number' validator.](Images/form_validators_number.png)

### Number range {#validators-number-range}

The validator checks if an entered number is within a
**specified number range**. The settings of the validator are as follows:

-   **Minimum**: The minimum value that can be accepted.
-   **Maximum**: The maximum value that can be accepted.
-   **Custom error message**: Custom error message that will be shown if the
    validation fails.

**The validator is available for the following form elements**:

-   ["Text"](https://docs.typo3.org/permalink/typo3/cms-form:form-elements-basic-elements-text@main)
-   ["Textarea"](https://docs.typo3.org/permalink/typo3/cms-form:form-elements-basic-elements-textarea@main)
-   ["Password"](https://docs.typo3.org/permalink/typo3/cms-form:form-elements-basic-elements-password@main)
-   ["Advanced password"](https://docs.typo3.org/permalink/typo3/cms-form:form-elements-advanced-elements-advanced-password@main)
-   ["Number"](https://docs.typo3.org/permalink/typo3/cms-form:form-elements-special-elements-number@main)

![In the Inspector - Settings of the 'Number range' validator.](Images/form_validators_numberRange.png)

### Regular expression {#validators-regular-expression}

The validator checks whether an **entered value** matches a
**specific regular expression**. The settings of the validator are as follows:

-   **Regular expression**: The regular expression used for validation.
-   **Custom error message**: Custom error message that will be shown if the
    validation fails.

Imagine that you want users to specify a domain name. The
resulting value of the field should contain only the domain, for example, "docs.typo3.org"
instead of "[https://docs.typo3.org](https://docs.typo3.org)". The regular expression for this
would be **/^\[a-z\]+.\[a-z\]+.\[a-z\]$/**.

**The validator is available for the following form elements**:

-   ["Text"](https://docs.typo3.org/permalink/typo3/cms-form:form-elements-basic-elements-text@main)
-   ["Textarea"](https://docs.typo3.org/permalink/typo3/cms-form:form-elements-basic-elements-textarea@main)
-   ["Password"](https://docs.typo3.org/permalink/typo3/cms-form:form-elements-basic-elements-password@main)
-   ["Advanced password"](https://docs.typo3.org/permalink/typo3/cms-form:form-elements-advanced-elements-advanced-password@main)
-   ["Telephone number"](https://docs.typo3.org/permalink/typo3/cms-form:form-elements-special-elements-telephone-number@main)
-   ["URL"](https://docs.typo3.org/permalink/typo3/cms-form:form-elements-special-elements-url@main)

![In the Inspector - Settings of the 'Regular Expression' validator.](Images/form_validators_regularExpression.png)

### Date range {#validators-date-range}

This validator checks whether an entered value is within a specific
**date range**. The range can be defined by specifying a **start** and/ or
**end date**. The settings of the validator are as follows:

-   **Start date**: The beginning of the date range (input: YYYY-MM-DD).
-   **End date**: The end of the date range (input: YYYY-MM-DD).
-   **Custom error message**: Custom error message that will be shown if the
    validation fails.

**The validator is available for the following form elements**:

-   ["Date"](https://docs.typo3.org/permalink/typo3/cms-form:form-elements-special-elements-date@main)

![In the Inspector - Settings of the 'Date range' validator.](Images/form_validators_dateRange.png)

### Number of submitted values {#validators-number-of-submitted-values}

The validator checks whether an entered value contains a specific number of
elements. The settings of the validator are as follows:

-   **Minimum**: The minimum number of values submitted.
-   **Maximum**: The maximum number of submitted values.
-   **Custom error message**: Custom error message that will be shown if the
    validation fails.

**The validator is available for the following form elements**:

-   ["Multi checkbox"](https://docs.typo3.org/permalink/typo3/cms-form:form-elements-select-elements-multi-checkbox@main)
-   ["Multi select"](https://docs.typo3.org/permalink/typo3/cms-form:form-elements-select-elements-multi-select@main)

![In the Inspector - Settings of the validator 'Number of submitted values'.](Images/form_validators_numberOfSubmittedValues.png)

### File size {#validators-file-size}

The validator checks the file size of a **file resource**. The settings of the
validator are as follows:

-   **Minimum**: The minimum acceptable file size (default: 0B).
-   **Maximum**: The maximum acceptable file size (default: 10M).

Use the format **B | K | M | G** (byte | kilobyte | megabyte | gigabyte) when
entering file sizes. For example: **10M** means **10 megabytes**. Please note
that the maximum file size also depends on the settings of your server
environment.

**The validator is available for the following form elements**:

-   ["File upload"](https://docs.typo3.org/permalink/typo3/cms-form:form-elements-advanced-elements-file-upload@main)
-   ["Image upload"](https://docs.typo3.org/permalink/typo3/cms-form:form-elements-advanced-elements-image-upload@main)

![In the Inspector - Settings of the 'File size' validator.](Images/form_validators_fileSize.png)

### Date/ Time {#validators-date-time}

The validator checks if an entered value is a valid **date and/ or time**.
The settings of the validator are as follows:

-   **Custom error message**: Custom error message that will be shown if the
    validation fails.