This feature is well established and works across many devices and browser versions. It’s been available across browsers since July 2015.
The validationMessage read-only property of the HTMLFieldSetElement interface returns a string representing a localized message that describes the validation constraints that the <fieldset> control does not satisfy (if any). This is the empty string as <fieldset> elements are not candidates for constraint validation (HTMLFieldSetElement.willValidate is false).
The empty string, "";
| Specification |
|---|
| HTML> # dom-cva-validationmessage-dev> |
| Desktop | Mobile | |||||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Chrome | Edge | Firefox | Opera | Safari | Chrome Android | Firefox for Android | Opera Android | Safari on IOS | Samsung Internet | WebView Android | WebView on iOS | |
validationMessage |
5 | 12 | 4 | ≤12.1 | 5 | 18 | 4 | ≤12.1 | 4 | 1.0 | 4.4 | 4 |
<fieldset>HTMLFieldSetElementHTMLFieldSetElement.willValidateHTMLFieldSetElement.validityHTMLFieldSetElement.checkValidity()HTMLFieldSetElement.reportValidity()HTMLFieldSetElement.setCustomValidity():valid and :invalid pseudo-classes
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https://developer.mozilla.org/en-US/docs/Web/API/HTMLFieldSetElement/validationMessage