Mac’s weird little “Default Browser Helper” plug‐in injected into all web browsers

Mac OS X 10.9 and newer bundles a new browser plug‐in. What is this newest Apple innovation used for? It is loaded in Opera, Firefox, and every other web browser. I’m no fan of strange new software appearing on my systems (especially plug‐ins and add‐ons). Thus, I did a little investigation of this new Mavericks “feature.”

Mac OS X 10.9 “Mavericks” introduced a new web browser plug‐in called “Default Browser Helper”. As usual, Apple have not been forthcoming with details about the purpose of its not‐very‐shiny new plug‐in. The only information offered by the plug‐in itself is “Provides information about the default web browser”. It is not clear who the information is provided to (web sites already know it) nor what it is for.

Update August 2016: The Default Browser plugin has been removed from macOS 10.12 “Sierra” and later. It would seem that Apple finally realized that it wasn’t all that useful.

The plug‐in is very simple. It only contains one test called isSafariDefaultBrowser, and when it sees any other web browser it will open the below dialog. Apple is thus able to prompt the users of other web browsers to set Safari as their default browser.

The plug‐in says it support an Internet media type (MIME) called application/apple-default-browser. Meaning that the plug‐in will only be invoked if the web browser comes across this media type. However, poking at the plug‐in with this content type does nothing. Nor have I found any product or website from Apple that seem to use this plug‐in.

Its hard to say when the plug‐in is intended to be used. However, the it smells suspiciously like a solution to an internal problem that should have been resolved in another way.

The current version of the plug‐in differs from Mac to Mac with the same operating system version and update level. There is no clear reason behind this.

The plug‐in can safely be disabled by users. As it is only used to promote the Safari web browser when Apple feels like it, users should not see any disadvantages to disabling or even removing it.