How does cloudflare detect the plugin is installed? about cloudflare-wordpress

[markjaquith]

The plugin tells WordPress to add an HTTP header:

cf-edge-cache: cache,platform=wordpress (if the response should use the cache)

or

cf-edge-cache: no-cache (if the response should not use the cache)

Cloudflare-WordPress/src/WordPress/Hooks.php

Lines 436 to 442 in 4ad24c8

	// add header unconditionally so we can detect plugin is activated
	$cache = apply_filters('cloudflare_use_cache', !is_user_logged_in());
	if ($cache) {
	header('cf-edge-cache: cache,platform=wordpress');
	} else {
	header('cf-edge-cache: no-cache');
	}

I suspect that when enabling APO on the Cloudflare side it just looks for this cf-edge-cache header to be present and have an expected value.