在 < iframe > 中，srcdoc = “ ...”和 src = “ data: text/html，...”有什么区别？

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The main difference is that the 'src' attribute contains the address of the document you are going to embed in the tag.

On the other hand 'srcdoc'attribute contains the HTML content of the page to show in the inline frame.

the main disadvantage of srcdoc is that it is not supported in all browsers whereas src is compatible with all the browsers.

for detailed explanation please go through the following link: https://developer.mozilla.org/en-US/docs/Web/HTML/Element/iframe

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From MDN :

^1. The content of the page that the embedded context is to contain. This attribute is expected to be used together with the sandbox and seamless attributes. If a browser supports the srcdoc attribute, it will override the content specified in the src attribute (if present). If a browser does NOT support the srcdoc attribute, it will show the file specified in the src attribute instead (if present).

So, the srcdoc attribute overrides the content embedded using src attribute.

Demo

Also, what you are saying about the following snippet data:text/html is called Data URI and it has limitations..

^2. Data URIs cannot be larger than 32,768 characters.

^{1. MDN, 2. MSDN}

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In your example the two forms are functionally identical. However, you can use both src and srcdoc attributes, allowing non-HTML5 browsers to use the src version, while HTML5 browsers can use the srcdoc version along with the sandbox and seamless attributes which offer more flexibility in how an iFrame is treated.

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srcdoc: The content of the page that the embedded context is to contain. This attribute is expected to be used together with the sandbox and seamless attributes. If a browser supports the srcdoc attribute, it will override the content specified in the src attribute (if present). If a browser does NOT support the srcdoc attribute, it will show the file specified in the src attribute instead (if present).

src: The URL of the page to embed.

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As of writing - srcdoc in Chrome (v36) allows the setting and fetching of cookies, whereas the use of src with data URL does not:

Uncaught SecurityError: Failed to read the 'cookie' property from 'Document': Cookies are disabled inside 'data:' URLs

This may or may not be important to you, but rules out the use of data URLs in the application I am building, which is a shame, as of course IE doesn't support srcdoc currently (v11).

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The other answers list some superficial differences, but really miss the mark of the key difference that explains why browsers/spec writers would essentially duplicate something that already exists:

<iframe src="data:...untrusted content" sandbox /> <- Secure in modern browsers, insecure in legacy browsers with no sandbox support

<iframe srcdoc="...untrusted content" sandbox /> <- Secure in modern browsers, secure (though non-functional) in legacy browsers

This new syntax provides content authors a way to protect their users, even when they may be using legacy browsers. Without it, content authors would be reluctant to use the sandbox feature at all, and it would not see use.

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Another noticeable difference is that src attributes with data-uri support URI percent-encoding rules while srcdoc doesn't as it supports regular html syntax,

these sources will yield differently:

<iframe srcdoc="<p>hello%20world</p><h1>give%0D%0Ame%0D%0Asome%24</h1>"></iframe>


<iframe src="data:text/html;charset=UTF-8,<p>hello%20datauri<p><h1>give%0D%0A me%0D%0Asome%24</h1>"></iframe>

I also noticed a difference in the parsing of js scripts inside the attributes value( it's probably more than just percentage-encoding ) but didn't figure the rule yet...

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Iframe with src attribute with HTML Content is cross domain,

But iframe with srcDoc attribute with HTML Content is not cross domain