There are many reasons a blog can be slow – from themes, plugins, loading scripts, images etc. Here are the most common and effective ways to speed up your blog.
Please note: do not use caching plugins. You can request caching (see the bottom of the page) once you’ve done everything else.
Compress and Resize Images
Optimizing Script Files
Scripts can often slow down the blog quite a bit. Search for a plugin that uses an external CDN which will increase the script’s loading speed.
You should also remove query strings from static resources (CSS, JS) with a query string remover plugin.
Activate one of the default themes (Twenty Thirteen, Fourteen or Fifteen). If the blog is now fast, the issue lies in the theme. We recommend finding a different theme that loads faster.
Disable all plugins and check if it speeds up the blog. If it does, the culprit is one of the plugins. Re-enable them one by one until you find the one that’s slowing the blog down.
If nothing of the above helped or you want to make it super-fast, you can request caching for the blog via the Report Problem button found on the blog's info page.
When cache is enabled, logged-in users see blog changes immediately, however, visitors will see it after one hour. You can purge cache so everyone sees changes immediately by installing the plugin Varnish HTTP Purge.
Blogs will be put into caching mode when traffic exceeds 4GB in the last four days or there are more than 40k requests in the last four days.