Over time a WordPress database collects data nothing uses. A leaner database backs up faster and can make admin screens quicker.
What builds up
- Post revisions — every saved draft of every post
- Auto-drafts and trash
- Spam and trashed comments
- Expired transients — temporary cached data plugins forgot to remove
- Tables left by deleted plugins
- Autoloaded options — settings loaded on every page, sometimes megabytes of them
Safe clean-up
- Back up the database first. How to export a database (backup with phpMyAdmin)
- Empty trash in Posts, Pages and Comments, and delete spam comments.
- Use a reputable database clean-up plugin to remove revisions, auto-drafts and expired transients.
- Optimise tables in phpMyAdmin. How to repair and optimise database tables
Limit future revisions
In wp-config.php:
define('WP_POST_REVISIONS', 5);Leftover plugin tables
Tables with a prefix matching a plugin you’ve deleted can usually be dropped, but only if you’re certain which plugin created them. When in doubt, leave them.
Large autoloaded options
In phpMyAdmin, run a query on wp_options for rows with autoload set to yes, ordered by the length of option_value. Huge rows usually belong to a specific plugin; deal with them through that plugin’s settings rather than deleting rows by hand.
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