How can I customize wp_footer, where is the code that controls what this function does?

I am using WordPress 2013 theme as a starting point for a new theme from scratch.

Under my themes folder, my footer.php theme looks like this. (Notice the final functionwp_footer().

    </div><!-- #main -->
    <footer id="colophon" class="site-footer" role="contentinfo">
        <?php get_sidebar( 'main' ); ?>

        <div class="site-info">
            <?php do_action( 'twentythirteen_credits' ); ?>
            <a href="https://wordpress.stackexchange.com/questions/121589/<?php echo esc_url( __("http://wordpress.org/', 'twentythirteen' ) ); ?>" title="<?php esc_attr_e( 'Semantic Personal Publishing Platform', 'twentythirteen' ); ?>">. <?php printf( __( 'Proudly powered by %s', 'twentythirteen' ), 'WordPress' ); ?></a>
    .       </div><!-- .site-info -->
        </footer><!-- #colophon -->
    </div><!-- #page -->

    <?php wp_footer(); ?>
</body>
</html>

The problem is that the function wp_footer() appears to be including plugins and code that I don’t want there. Specifically, the search widget.

I reviewed this article. Also the codex, directs me to the directory wp-includes/general-template.php, which does not tell me anything about which template tags it might be requiring (I was expecting it would require the search widget).

How does one customize the behavior of wp_footer? Where (in the file directory) should one look to see what html/php that wp_footer is dynamically producing?

This could be multiple things. I’m not sure what the credits do. However, the chance is quite big that the search field is being created by a widget, shown in the get_sidebar('main'). Under “Appearance” > “Widgets”, you should be able to find more information.

The template being called is probably sidebar-main.php.

If it is a specific plugin creating the output into the wp_footer() (which I think is unlikely), you could probably find it with add_action('wp_footer', 'the_function');, “the_function” being the function called.

This specific action hooks a function into the wp_footer().

wp_footer is mainly used to load javascripts and other necessities, but not so much to add extra content.

I hope this clears things up for you a bit. In case it didn’t, I’d be glad to clarify as much as possible.