The way @sam presented it works:
<form name="ExpressaoRegular">
Por favor, preencha pelo menos 3 caracteres entre letras e números.
<input type="text" name="teste"
pattern=".{3,}">
<input type="submit">
</form>
Unless there are multiple lines (multiline), then you can
utilise [/s/S]{3,}
And if you don’t want to include special characters and only space, letters and numbers:
<form name="ExpressaoRegular">
Por favor, preencha pelo menos 3 caracteres entre letras e números.
<input type="text" name="teste"
pattern="[\w\d\s]{3,}">
<input type="submit">
</form>
Try it like this
.{3,}
– Sam
does not work regex must accept blanks
– Cleber Castiglioni
the dot accepts any character.
– Sam