Does opacity:0 have exactly the same effect as visibility:hidden

Question

If so, does it effectively deprecate the visibility property?

(I realize that Internet Explorer does not yet support this CSS2 property.)
Comparisons of layout engines

See also: What is the difference between visibility:hidden and display:none

Ferbam

And how about taborder? If visible=false then the control does not get any focus, but if opacity is 0 maybe the tab key still iterates between the controls? – Kirman

It would be an interesting test case to see how a transparent control might get focus. – Ferbam

I tried that, (FF3). An input element with opacity:0 does receive focus, per the taborder, though there is no visual indication. The cursor just disappears. Whatever you type is entered into the value of the input element. Pressing tab again moves on to the next field. Interesting. – Ferbam

Answer 1

Here is a compilation of verified information from the various answers.

Each of these CSS properties is unique. In addition to rendering an element not visible, they have the following additional effect(s):

1. Collapses the space that the element would normally occupy
2. Responds to events (e.g., click, keypress)
3. Participates in the taborder

                     collapse events taborder
opacity: 0              No     Yes     Yes
visibility: hidden      No     No      No
visibility: collapse   Yes*    No      No
display: none          Yes     No      No

* Yes inside a table element, otherwise No.

Ferbam

I tried to follow the Markdown documentation here: daringfireball.net/projects/markdown/syntax – Ferbam

Okay, so SO intentionally does not support <table>. So I made it ascii. – Ferbam

Also, with "opacity: 0" Flash objects are rendered, and sprite's constructor is triggered, but with "visibility: hidden" not. – Damsel

If your radio/checkboxes are not working with visibility:hidden, then you'd need to use opacity: 0 instead for it to detect the mouse click. – Coit

@ChrisNoe: thanks for the summary. One thing you might want to add: I just researched how to make a parent node invisible but child nodes still visible, the result: no chance for visible children: opacity:0 or display:none, but if you use visibility: hidden you can make children visible with visibility: visible – Micro

Your are CSS expert! – Grasmere

@ChrisNoe Good answer, but I recommend also mentioning how performance is affected by these properties. Opacity is the only one not triggering a reflow: csstriggers.com/opacity. – Gerdi

Answer 2

No.

Elements with opacity create new stacking context.

Also, CSS spec doesn't define this, but elements with opacity:0 are clickable, and elements with visibility:hidden are not.

Dissatisfactory

Answer 3

No it does not. There is a big difference. They are similar because you can see through the element if visibility is hidden or opacity is 0, however

opacity: 0 : you can not click on elements behind it.

visibility: hidden : you can click on elements behind it.

Mongolic

"No it does not"? Is this meant as an answer to the Question, or as a response to one of the existing Answers? If it is the later, then it should be added as a comment under the answer it addresses. – Ferbam

This is an answer to "Does opacity:0 have exactly the same effect as visibility:hidden ?".... was that not obvious though ? – Mongolic

Answer 4

There are many differences between visibility and opacity. Most of the answers mention some differences, but here is a complete list.

1. opacity does not inherit, while visibility does

2. opacity is animatable while visibility is not.
   (Well, technically it is, but there is simply no behaviour defined for, say, "37% collapsed and 63% hidden", so you can consider this as non-animatable.)

3. Using opacity, you can not make a child element more opaque than its parent. E.G. if you have a p with color:black and opacity:0.5, you can not make any of its children fully black. Valid values for opacity are between 0 and 1, and this example would require 2!
   Consequently, according to Martin's comment, you can have a visible child (with visibility:visible) in an invisible parent (with visibility:hidden). This is impossible with opacity; if a parent has opacity:0; its children are always invisible.

4. Kornel's answer mentions that opacity values less than 1 create their own stacking context; no value for visibility does.
   (I wish I could think of a way to demonstrate this, but I can't think of any means to show the stacking context of a visibility:hidden element.)

5. According to philnash's answer, elements with opacity:0 are still read by screen readers, while visible:hidden elements are not.

6. According to Chris Noe's answer, visibility has more options (such as collapse) and elements that are not visible no longer respond to clicks and cannot be tabbed to.

(Making this a community wiki, since borrowing from the existing answers wouldn't be fair otherwise.)

Additory

Answer 5

I'm not entirely sure of this, but I think screen readers don't read things that are set to visibility hidden, but they may read things regardless of their opacity.

That's the only difference I can think of.

Mayweed

How would that effect the result then? Perhaps in terms of what is included in the DOM? My test cases show that Mozilla is not throwing away visibility:hidden elements. – Ferbam

The elements would be in the DOM regardless of CSS style, I mean that blind users using screen reader software may have text in the opacity:0 element read to them, whereas they wouldn't if the same element had visibility:hidden. It's an accessibility concern really, as the result is different. – Mayweed

useful point, it is one of the result of setting visibility to hidden, but this is just the the tip of iceberg. More specifically, visibility:hidden makes it (seemingly) disappear from dom, while still maintaining its layout on page. – Mongolic

Answer 6

Im not sure entirely, but this is how i do cross browser transparency:

opacity: 0.6;
-moz-opacity: 0.6;
filter: alpha(opacity=60);

objects with Visibility:hidden still have shape, they just arent visible. opacity zero elements can still be clicked and react to other events.

Foolery

What does it mean to have shape and be invisible? – Ferbam

@chris, it means that they still take up the space on the page – Dysarthria

opacity is used to decide how the element is drawn ontop of the background. With opactiy set to 0 the element naturally takes space but nothing is drawn because 0% of the element colour is mixed with 100% of the background resulting in nothing new appearing. hidden and similar friends mean the element is skipped when drawing takes place. – Guard

Answer 7

While making a userstyle that affects elements in a contenteditable, I noticed that if you set something to visibility: hidden, then the input caret doesn't really want to interact with it. Eg if you have

<div contenteditable><span style='visibility: hidden;'></span></div>

...then it seems if you focus that div/span, you can't actually type in it. Whereas with opacity: 0 it seems you can. I haven't tested this extensively, but figured it was worth mentioning this here as nobody else on this page has talked about the effects on text input. This seems possibly related to the events stuff mentioned above though.

Indophenol

Answer 8

What Phil says is true.

IE supports opacity though:

filter:alpha(opacity=0);

Chasse

Answer 9

The properties have different semantic meanings. While semantic CSS sounds like it may be silly, as other users have mentioned it has an impact on devices like screen readers -- where semantics impact the accessibility of a page.

Loch