In short
Drift usually comes from third-party scripts, heavier images, new sections, analytics tags, CSS and JavaScript growth, font changes, or CMS content that bypasses the original performance budget.
The fix is not a one-time speed pass. It is a budget, release checks, ownership, and regular review of the pages that matter commercially.
Where it bites
Performance drift bites when paid traffic gets more expensive, organic pages lose ground, mobile users abandon forms, or an editor unknowingly turns a key landing page into a heavy page.
What to check
- Which page templates have slowed down since launch?
- Which scripts, images, fonts, or embeds were added without a budget check?
- Does the deployment pipeline catch Core Web Vitals or page-weight regressions?
Common questions
What is performance drift?
Performance drift is the gradual decline in page speed and responsiveness as a website accumulates scripts, assets, content changes, and dependencies after launch.
Why does performance drift happen?
It happens because teams keep adding features, tags, embeds, images, and content without enforcing the original performance budget.
What should you check first for performance drift?
Compare current Core Web Vitals, page weight, script cost, image weight, and key templates against the launch baseline or performance budget.