I'm developing a site for a client that will be part of a multisite. I've added a number of new users, but when those users try to confirm their accounts they get the dreaded "white screen of death" and their accounts aren't activated.

Can anyone help me figure out why this is happening?


[note: I solved the problem before asking this question and thought others would find my research/solution helpful, see Can I answer my own question?]

The site in question uses a custom theme and site-specific plugin (that registers custom post types, custom taxonomies, etc), both of which I've written.

It turns out that the wp-activate.php bootstrap results in plugins not being loaded...which came as quite a shock to me (and is not documented anywhere that I can find).

My theme's header.php calls one of the methods defined in the site-specific plugin. Since plugins aren't loaded when wp-activate.php runs, that method isn't defined and PHP dies. To make matters worse, the wp-activate.php bootstrap also disables PHP error messages (even when WP_DEBUG is set to true), hence, the white screen of death :-(


To solve the problem, I hooked into activate_header (the first hook fired after the wp-active.php bootstrap) and loaded the site-specific plugin myself, as follows:

add_action ('activate_header', 'load_site_specific_plugin') ;

load_site_specific_plugin ()
    if (wp_installing ()) {
        require_once (WP_PLUGIN_DIR . 'path to site-specific plugin') ;

    return ;

See the Gory Deatils section below for why I tested wp_installing() before calling require_once().

Alternate Solution

Another solution would be to add a header-wp-activate.php (that doesn't rely on any methods defined in the site-specific plugin) to my theme. For my purposes, that didn't seem to be the right choice, but might be for others.

Gory Details

I have no idea why it was decided that wp-activate.php should not load plugins. But here's a description of the relevant parts of the wp-activate.php bootstrap, and why it results in plugins not being loaded and PHP error messages to not be displayed.

First, wp-activate.php begins with:

define( 'WP_INSTALLING', true );

Defining WP_INSTALLING as true has cascading effects throughout the wp-activate.php bootstrap. Most importantly for the problem I was experiencing, is that wp_get_active_and_valid_plugins() (which is called in wp-settings.php as part of the bootstrap) contains the following:

if ( empty( $active_plugins ) || wp_installing() )
    return array();

Hence, the bootstrap thinks the site doesn't use any plugins even tho get_option('active_plugins') returns a non-empty array.

To understand why no PHP errors were output when WP died while trying to load my theme's header.php (again, even tho I have define ('WP_DEBUG', true) ;), we have to look at the way wp_debug_mode() is written. wp_debug_mode() is called before the call to wp_get_active_and_valid_plugins() during the wp-activate.php bootstrap and contains the following:

if ( defined( 'XMLRPC_REQUEST' ) || defined( 'REST_REQUEST' ) || ( defined( 'WP_INSTALLING' ) && WP_INSTALLING ) || wp_doing_ajax() ) {
    @ini_set( 'display_errors', 0 );

So, not only does the wp-activate.php bootstrap not load any plugins, it also causes PHP errors that result from that fact to not be displayed; hence, the white screen of death! Argh!!!

Can anyone explain to my why it was decided that the wp-activate.php bootstrap should act this way?

TL;DR: see the comment I left on a thread about the Nextgen Bootstrap/Load Feature Project on Make WordPress Core.

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