First Input Delay (FID)
First Input Delay (FID) is a legacy Core Web Vitals metric that measured delay on the user's first interaction only. In March 2024, Google replaced FID with Interaction to Next Paint (INP), which measures responsiveness across interactions throughout the session.
FID is deprecated and most reporting should use Interaction to Next Paint (INP) instead.
The Metric Evolution
FID captured only the first input delay, which could miss responsiveness issues that happen later (filters, cart updates, checkout flows, account dashboards). INP reflects what users experience across interactions over the full session.
| Metric Parameter | Operational Scope | Current Engineering Status |
|---|---|---|
| FID (Legacy) | Benchmarked strictly the delay to the handler start of the single initial interaction point. | Fully Deprecated (March 2024) |
| INP (Active) | Aggregates the worst interaction latency mapped out continuously over the entire session (input-to-paint). | Prime Active CWV Factor |
Legacy Reporting Visibility
You may still encounter FID in older tooling and reports:
- Historical exports from PageSpeed/Lighthouse.
- Older dashboards and documentation.
If you see FID in an audit, treat it as historical context and focus remediation on INP.
Migration & Action Workflow
- Replace FID targets in scorecards with INP targets.
- Prefer field data (CrUX/Search Console) for your "real users" view.
- In lab testing, use Total Blocking Time (TBT) and long-task analysis to find main-thread issues.
Persistent Value Paradigms
Even though FID is deprecated, the same engineering patterns still help:
- Reduce long tasks from heavy JavaScript.
- Delay or remove non-essential third-party scripts.
- Keep backend responses fast for interactive actions (AJAX, cart updates, filters).
Historical Thresholds (For Archive Only)
FID Historical Boundaries (Deprecated):
Good: ≤ 100 ms
Needs Improvement: 100-300 ms
Poor: > 300 ms
Active Interactivity Replacement (INP):
INP Good Threshold: ≤ 200 ms