Embedding an Applet in HTML

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PaintApplet from the previous lesson compiles into a plain .class file - on its own, nothing about it says "web page." What actually told an old browser to load it, size it, and drop it into the page was a piece of HTML markup. This lesson shows you that markup so you can recognize it in old code and textbooks. No new Java code is introduced here.

Read this as history, not as a how-to: everything on this page describes how applets used to be embedded. None of it will make an applet run in any browser released after roughly 2015-2016, regardless of which JDK you have installed - browsers dropped the plugin architecture (NPAPI) that this markup depended on industry-wide around that time, well before the JDK itself deprecated the Applet API. This lesson exists so the markup looks familiar if you come across it, not as deployment guidance.

The Classic <applet> Tag

The original, simplest way to embed PaintApplet looked like this:

<applet code="PaintApplet.class" width="400" height="300">
  Your browser cannot run Java applets.
</applet>

Attribute / content	Meaning
`code`	The compiled class to load - here, `PaintApplet.class`, produced by `javac` as in the previous lesson.
`width`	The width, in pixels, of the rectangular area the browser reserves for the applet - this is exactly what `PaintApplet.getWidth()` would report at runtime.
`height`	The height, in pixels, of that same area - what `getHeight()` would report.
Text between the tags	Fallback content shown only by browsers that don't understand the `<applet>` tag at all (or have no Java plugin) - conceptually similar to alt text on an `<img>`.

This is exactly the markup you already used with appletviewer in Environment Setup - appletviewer understands this tag and gives you a working preview window, even though a real browser today would simply render the fallback text (or nothing at all).

The Later <object> / <embed> Variants

As browsers evolved, the plain <applet> tag was gradually superseded by more generic <object> and <embed> tags carrying MIME-type parameters that pointed at the Java plugin, often written together so different browsers could pick whichever one they supported:

<object classid="clsid:8AD9C840-044E-11D1-B3E9-00805F499D93"
        width="400" height="300">
  <param name="code" value="PaintApplet.class">
  <embed type="application/x-java-applet"
         code="PaintApplet.class" width="400" height="300">
  </embed>
  Your browser cannot run Java applets.
</object>

Functionally this aimed at the same goal as the plain <applet> tag - load PaintApplet.class into a 400×300 area - but with browser-specific plugin-detection plumbing bolted on. It is just as dead as the tag it replaced; every browser that could run either one is long gone from general use.

Both forms shown on this page are historical reference only. If you want to actually see PaintApplet render, use appletviewer with the plain <applet> markup and a JDK 8 install, exactly as shown in Environment Setup - not by opening either snippet above in an actual browser.

Recap: The <applet code="..." width="..." height="..."> tag was the classic way to embed a compiled applet class in a page, later joined by <object>/ <embed> variants with plugin-detection parameters. Both are dead in every current browser; only appletviewer still understands this markup today.

Next steps: So far PaintApplet has used plain AWT. See how Swing's richer component model changes the picture in JApplet and Swing Components.

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