I had a client recently who (for reasons exclusively to do with the inexperience of their website’s designer) turned off one of the SEO plugins I had installed and configured for them.
It happened shortly after I carried out an initial SEO overhaul on their site, so gives us a valuable insight into the effect of getting SEO done, and the removing it again.
It’s a very small (and brand new company), but you can see the effects in this graph – taken directly from Google Search Console.
Initially after my work their SEO stats began to shoot up, gaining traction and upward momentum. Immediately after deactivating just one plugin it plummeted back to its original position.
This didn’t use to happen so quickly. If you took SEO work off a site, or just fell behind with updates and changes to best practice, things would trail off over time. It now appears not having the very best SEO at all times leads to an immediate decrease in SEO authority. Because so many website owners (your competitors!) invest in SEO these days it means any time you don’t have it working, they can rise above you in the rankings.
But other SEO professionals have tried the same thing (turning off a single SEO plugin on their own testing sites) and see the same result. The drop is nearly immediate.