embed vs. Iframe?

<iframe>

The iframe element represents a nested browsing context. HTML 5 standard - "The <iframe> element"

Primarily used to include resources from other domains or subdomains but can be used to include content from the same domain as well. The <iframe>'s strength is that the embedded code is 'live' and can communicate with the parent document.

<embed>

Standardised in HTML 5, before that it was a non standard tag, which admittedly was implemented by all major browsers. Behaviour prior to HTML 5 can vary ...

The embed element provides an integration point for an external (typically non-HTML) application or interactive content. (HTML 5 standard - "The <embed> element")

Used to embed content for browser plugins. Exceptions to this is SVG and HTML that are handled differently according to the standard.

<object>

The <object> element can represent an external resource, which, depending on the type of the resource, will either be treated as an image, as a nested browsing context, or as an external resource to be processed by a plugin. (HTML 5 standard - "The <object> element")

Conclusion

Unless you are embedding SVG or something static you are probably best of using <iframe>. To include SVG use embed (if I remember correctly <object> won't let you script). Honestly I don't know why you would use <object> unless for older browsers or flash (that I don't work with).

EMBED can work like magic. This is the one used by you tube and most web sites for adding videos to your site.

IFRAME is used by amazon. It can break your site. Be careful using it. Not rec.

Often, because it will break sites, I add the IFRAME to the bottom of my web page.

Lately, there are a lot of problems with the IFRAMES from amazon. Sadly, this situation is getting serious. I will probably go in and get rid of most of mine.