What's the valid way to include an image with no src?

Solution 1:

Another option is to embed a blank image. Any image that suits your purpose will do, but the following example encodes a GIF that is only 26 bytes - from http://probablyprogramming.com/2009/03/15/the-tiniest-gif-ever

<img src="data:image/gif;base64,R0lGODlhAQABAAD/ACwAAAAAAQABAAACADs=" width="0" height="0" alt="" />

Edit based on comment below:

Of course, you must consider your browser support requirements. No support for IE7 or less is notable. http://caniuse.com/datauri

Solution 2:

While there is no valid way to omit an image's source, there are sources which won't cause server hits. I recently had a similar issue with iframes and determined //:0 to be the best option. No, really!

Starting with // (omitting the protocol) causes the protocol of the current page to be used, preventing "insecure content" warnings in HTTPS pages. Skipping the host name isn't necessary, but makes it shorter. Finally, a port of :0 ensures that a server request can't be made (it isn't a valid port, according to the spec).

This is the only URL which I found caused no server hits or error messages in any browser. The usual choice — javascript:void(0) — will cause an "insecure content" warning in IE7 if used on a page served via HTTPS. Any other port caused an attempted server connection, even for invalid addresses. (Some browsers would simply make the invalid request and wait for them to time out.)

This was tested in Chrome, Safari 5, FF 3.6, and IE 6/7/8, but I would expect it to work in any browser, as it should be the network layer which kills any attempted request.

Solution 3:

These days IMHO the best short, sane & valid way for an empty img src is like this:

<img src="data:," alt>
or
<img src="data:," alt="Alternative Text">

The second example displays "Alternative Text" (plus broken-image-icon in Chrome and IE).

"data:," is a valid URI. An empty media-type defaults to text/plain. So it represents an empty text file and is equivalent to "data:text/plain,"

Solution 4:

I recommend dynamically adding the elements, and if using jQuery or other JavaScript library, it is quite simple:

• http://api.jquery.com/appendTo/
• http://api.jquery.com/prependTo/
• http://api.jquery.com/html/

also look at prepend and append. Otherwise if you have an image tag like that, and you want to make it validate, then you might consider using a dummy image, such as a 1px transparent gif or png.

Solution 5:

I haven't done this in a while, but I had to go through this same thing once.

<img src="about:blank" alt="" />

Is my favorite - the //:0 one implies that you'll try to make an HTTP/HTTPS connection to the origin server on port zero (the tcpmux port?) - which is probably harmless, but I'd rather not do anyways. Heck, the browser may see the port zero and not even send a request. But I'd still rather it not be specified that way when that's probably not what you mean.

Anyways, the rendering of about:blank is actually very fast in all browsers that I tested. I just threw it into the W3C validator and it didn't complain, so it might even be valid.

Edit: Don't do that; it doesn't work on all browsers (it will show a 'broken image' icon as pointed out in the comments for this answer). Use the <img src='data:... solution below. Or if you don't care about validity, but still want to avoid superfluous requests to your server, you can do <img alt="" /> with no src attribute. But that is INVALID HTML so pick that carefully.

Test Page showing a whole bunch of different methods: http://desk.nu/blank_image.php - served with all kinds of different doctypes and content-types. - as mentioned in the comments below, use Mark Ormston's new test page at: http://memso.com/Test/BlankImage.html