How can I make an entire HTML form "readonly"?

Question

Wrap the input fields and other stuff into a <fieldset> and give it the disabled="disabled" attribute.

Example (http://jsfiddle.net/7qGHN/):

<form>
    <fieldset disabled="disabled">
        <input type="text" name="something" placeholder="enter some text" />
        <select>
            <option value="0" disabled="disabled" selected="selected">select somethihng</option>
            <option value="1">woot</option>
            <option value="2">is</option>
            <option value="3">this</option>
        </select>
    </fieldset>
</form>

Not all form elements can be set to readonly, for example:

• checkboxes
• radio boxes
• file upload
• ...more..

Then the reasonable solution would be to set all form elements' disabled attributes to true, since the OP did not state that the specific "locked" form should be sent to the server (which the disabled attribute does not allow).

Another solution, which is presented in the demo below, is to place a layer on top of the form element which will prevent any interaction with all the elements inside the form element, since that layer is set with a greater z-index value:

DEMO:

var form = document.forms[0], // form element to be "readonly"
    btn1 = document.querySelectorAll('button')[0],
    btn2 = document.querySelectorAll('button')[1]

btn1.addEventListener('click', lockForm)
btn2.addEventListener('click', lockFormByCSS)

function lockForm(){
  btn1.classList.toggle('on');
  [].slice.call( form.elements ).forEach(function(item){
      item.disabled = !item.disabled;
  });
}

function lockFormByCSS(){
  btn2.classList.toggle('on');
  form.classList.toggle('lock');
}

form{ position:relative; } 
form.lock::before{
  content:'';
  position:absolute;
  z-index:999;
  top:0;
  right:0;
  bottom:0;
  left:0;
}

button.on{ color:red; }

<button type='button'>Lock / Unlock Form</button>
<button type='button'>Lock / Unlock Form (with CSS)</button>
<br><br>
<form>
  <fieldset>
    <legend>Some Form</legend>
    <input placeholder='text input'>
    <br><br>
    <input type='file'>
    <br><br>
    <textarea placeholder='textarea'></textarea>
    <br><br>
    <label><input type='checkbox'>Checkbox</label>
    <br><br>
    <label><input type='radio' name='r'>option 1</label>
    <label><input type='radio' name='r' checked>option 2</label>
    <label><input type='radio' name='r'>option 3</label>
    <br><br>
    <select>
      <option>options 1</option>
      <option>options 2</option>
      <option selected>options 3</option>
    </select>
  </fieldset>
</form>

You can use this function to disable the form:

function disableForm(formID){
  $('#' + formID).children(':input').attr('disabled', 'disabled');
}

See the working demo here

Note that it uses jQuery.

On the confirmation page, don't put the content in editable controls, just write them to the page.

There is no built-in way that I know of to do this so you will need to come up with a custom solution depending on how complicated your form is. You should read this post:

Convert HTML forms to read-only (Update: broken post link, archived link)

EDIT: Based on your update, why are you so worried about having it read-only? You can do it via client-side but if not you will have to add the required tag to each control or convert the data and display it as raw text with no controls. If you are trying to make it read-only so that the next post will be unmodified then you have a problem because anyone can mess with the post to produce whatever they want so when you do in fact finally receive the data you better be checking it again to make sure it is valid.