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Editorial Team
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Asked: 2026-05-27T05:16:18+00:00

As the title says, are there limits and/or prohibited characters for form field names

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As the title says, are there limits and/or prohibited characters for form field names?

  • If I use an sha512() hash for field name, are there drawbacks to this (it’s pretty lengthy)?
  • Or, are there any drawbacks when using -:x:©:y: as field name?
  • Or, may I use a serialized array for field name?
  • Or, what if the field contains a space character?
  • What about “/downloads/ready/games/” as a key?

I bet, this isn’t HTML specific, but more PHP (scripting language) specific, whether after the posting, the values can be read. Theoretically, it may also apply to array keys in general.

One more thing I thought about, the usage of “readable” form fields has become so popular/mainstream because forms are mostly used for storing data inside a database, where field name resembles the column within database. Correct me if I’m wrong.

So, yes, am I free to use whatever I want in these forms, or I may end up with errors/unreadable data?

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1 Answer

  1. Editorial Team

    The HTML5 spec defines the allowed values for name attributes on <form> elements.

    The value must not be the empty string, and the value must be unique amongst the form elements in the forms collection that it is in, if any.

    Of course it also defines allowed values for the name attribute on form controls (<input>, <textarea>, &c.) (emphasis added).

    4.10.19.1 Naming form controls

    The name content attribute gives the name of the form control, as
    used in form submission and in the form element’s elements object.
    If the attribute is specified, its value must not be the empty string.

    Any non-empty value for name is allowed, but the names “_charset_” and “isindex” are special:

    isindex
    This value, if used as the name of a Text control that is the first control in a form that is submitted using the
    application/x-www-form-urlencoded mechanism, causes the submission
    to only include the value of this control, with no name.

    _charset_
    This value, if used as the name of a Hidden control with no value attribute, is automatically given a value during
    submission consisting of the submission character encoding.

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