Short answer: no, not in the way most people assume. A properly deactivated plugin doesn't execute any code when a visitor loads your site -- WordPress only runs the hooks and functions of plugins that are actually active. If a plugin is off, its PHP isn't running, and it isn't touching your page load speed at all.

But "it's not slowing anything down" isn't the same as "it's free to leave sitting there." A few things deactivated plugins can quietly cost you:

Security surface that never goes away. An inactive plugin's files are still sitting on your server. Outdated, abandoned plugins are one of the most common ways WordPress sites get compromised -- and a plugin doesn't need to be running to be a vulnerability if its files are still reachable. Deactivated isn't the same as gone.

Orphaned database bloat. Well-built plugins clean up after themselves on deactivation. Plenty don't. Leftover database tables, options, and scheduled cron jobs from a plugin you turned off a year ago can sit there indefinitely, adding up over time even though the plugin itself isn't "running."

Admin clutter that costs you time, not the server. Every deactivated plugin sitting in your plugins list is one more thing to scroll past, one more thing a future developer has to figure out is safe to delete, one more question mark during an audit.

The real fix isn't "deactivate and forget" -- it's actually deleting what you're not using. We went through exactly this kind of cleanup pass on our own WordPress infrastructure recently: auditing every plugin, removing what had outlived its purpose, and confirming nothing was quietly costing us security exposure or admin confusion for no benefit. It's not glamorous work, but it's the kind of thing that keeps a WordPress site fast and stable years in, instead of slowly accumulating risk nobody's tracking.

If your plugins list looks like a graveyard and you're not sure what's actually safe to remove, that's exactly the kind of mess our WordPress Emergency Fix Support team sorts through regularly. And if performance is the actual concern driving the question, worth knowing the real bottlenecks are almost always active plugins doing too much, not inactive ones doing nothing -- which is exactly what we audit for as part of Foxco Fast WordPress Hosting.