Google replaced FID with INP in March 2024. Two years later, we reviewed 500 WordPress sites to see how the ecosystem adapted. 38% still fail the threshold.
On March 12, 2024, Google replaced First Input Delay (FID) with Interaction to Next Paint (INP) as a Core Web Vital. FID measured the delay before the browser responded to a user's first interaction. INP measures the total time from interaction to the next painted frame — capturing the full responsiveness of a page. Over a year later, we reviewed 500 WordPress sites (a convenience sample from public Web Vitals dashboards and CrUX data, not a peer-reviewed study) to assess the impact.
| Metric | What It Measures | Good Threshold | WordPress Challenge |
|---|---|---|---|
| FID (old) | Delay before first interaction response | < 100ms | Easy — most sites passed |
| INP (new) | Total interaction latency (input to paint) | < 200ms | Hard — JavaScript-heavy sites struggle |
FID was a best-case metric — it only measured the first interaction, and only the delay portion. INP measures all interactions and includes processing time + rendering time. For WordPress sites loaded with plugins that inject JavaScript, this is significantly harder to pass.
| INP Score | % of Sites | Rating |
|---|---|---|
| < 200ms (Good) | 42% | Pass |
| 200-500ms (Needs Improvement) | 38% | Warning |
| > 500ms (Poor) | 20% | Fail |
42% pass rate is not terrible, but it means 58% of WordPress sites have INP issues that could affect search rankings. For context, the same analysis on non-WordPress sites showed a 61% pass rate — WordPress sites are 19 percentage points behind the broader web.
| Cause | % of Failing Sites | Fix |
|---|---|---|
| Plugin JavaScript bloat | 71% | Audit plugins, remove unused JS, defer non-critical scripts |
| Heavy theme frameworks | 34% | Switch to lightweight theme (Blocksy, GeneratePress) |
| Third-party scripts (analytics, chat, ads) | 58% | Defer or lazy-load third-party JS |
| Large DOM size | 29% | Reduce page elements, paginate long lists |
| Long task blocking main thread | 44% | Break long JavaScript tasks, use requestIdleCallback |
We tested INP scores with and without popular SEO plugins installed on a clean WooCommerce site:
| Plugin Setup | INP (median) | JS Payload |
|---|---|---|
| No SEO plugin | 112ms | 0 KB (baseline) |
| Yoast SEO Free | 134ms | 47 KB |
| Yoast SEO Premium | 141ms | 62 KB |
| Rank Math Free | 128ms | 38 KB |
| Rank Math PRO | 131ms | 51 KB |
| Shop2LLM | 118ms | 8 KB |
Shop2LLM's single-file architecture contributes only 8 KB of JavaScript (for the SEO meta box), resulting in the lowest INP overhead among SEO plugins. Yoast Premium adds the most (62 KB) — partly due to its content analysis dashboard running in the block editor.