Placeholder

<field type="text" hint="Placeholder text goes here" />

In non supported browsers set color of placeholder by using css on placeholder class. For example

.placeholder{
      color : grey;
}

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Required

<field type="text" required="true" />
<field type="text" required="1" />
<field type="text" required="required" />

Browsers which supports HTML5 provide feedback whose UI depends upon browser itsef. But in non supported browsers feedback is provided by adding required and invalid class to the field. So developers can set css to display invalid or required elements in highlight. For example

.required, .invalid{
      colr : red;
}

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Autofocus

<field type="text" autofocus="true" />
<field type="text" autofocus="1" />
<field type="text" autofocus="on" />

First element with autofocus attribute get focus.

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Multiple

<field type="email" multiple="true" />
<field type="email" multiple="1" />
<field type="email" multiple="multiple" />

<field type="file" multiple="true" />
<field type="file" multiple="1" />
<field type="file" multiple="multiple" />

Fallback is provided for only multiple emails only.

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Formnovalidate

Although it can't be used in xml with any field, but it affect other fields. So we can do as

<input type="submit" formnovalidate>

List

<field type="text">
      <option value="Option 1">Opt1</option>
      <option value="Option 2">Opt2</option>
      <option value="Option 3">Opt3</option>
</field>

This attribute still doesn't have fallback.

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Autocomplete

<field type="text" autocomplete="off" />
<field type="text" autocomplete="0" />
<field type="text" autocomplete="false" />
<field type="text" autocomplete="name" />

Depends upon browser for the data.

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Spellcheck

<field type="text" spellcheck="off" />
<field type="text" spellcheck="0" />
<field type="text" spellcheck="false" />

No Fallback

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Inputmode

<field type="text" inputmode="latin-prose" />
<field type="text" inputmode="default" />
<field type="text"  inputmode="default latin-prose"  />

No Fallback

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Accept

<field type="file" accept="text/js" />

No Fallback

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Dirname

<field type="text" dirname />

No Fallback.

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