First Input Delay (FID) was a Core Web Vitals metric. It measured the time between a user’s first interaction with a page and the moment the browser could start running the event handlers. FID is historical. Since March 12, 2024, Interaction to Next Paint (INP) has taken its place as a Core Web Vital.
At a glance
- Measures
- Wait from the first interaction until the browser can start processing event handlers
- “Good” threshold
- 100 ms or less
- Assessment
- 75th percentile of page views
- Data source
- Field data only, needs a real user
- Status
- Core Web Vital until March 12, 2024, replaced by INP; Chrome tools ended FID support on September 9, 2024
Last checked:
What did FID measure?
Only the wait before the first interaction (click, tap or key press) was captured. The time the event handlers ran and the time until something visible changed were not part of it. Scrolling and zooming were excluded. A value of 100 milliseconds or less counted as good, assessed at the 75th percentile of page views. FID could only be collected from real users, as field data.
Why was it replaced?
Google’s announcement says INP replaces FID and that FID is deprecated. INP observes all interactions of a visit and measures up to the next painted frame. web.dev announced a transition period of about six months with the INP launch: developers had until September 9, 2024 to move to INP, after which Chrome tools no longer supported FID.
- Google introduces Web Vitals. The first Core Web Vitals are LCP, FID and CLS.Source: blog.chromium.org
- Google announces a page experience ranking signal that combines Core Web Vitals with existing signals.Source: developers.google.com
- Google sets the date: the signals are to be used in ranking from May 2021.Source: developers.google.com
- Postponed: gradual rollout from mid-June 2021, full effect only by the end of August 2021.Source: developers.google.com
- Page experience update for mobile: Core Web Vitals become part of the ranking systems.Source: developers.google.com
- Page experience update for desktop, using the same Core Web Vitals thresholds as on mobile.Source: status.search.google.com
- INP is no longer experimental. Google announces that INP will replace FID as a Core Web Vital in March 2024.Source: web.dev
- INP replaces FID. Since then the Core Web Vitals are LCP, INP and CLS. Articles citing “FID 100 ms” as a threshold are out of date.Source: web.dev
- Chrome tools end support for FID.Source: web.dev
End of the mobile rollout: Google says “between June and August 2021”; the often-cited date of September 2, 2021 comes only from a Google Search Central post on X. Last checked: .
What applies today?
Advice written about FID can usually be applied to INP. The causes are mostly the same: long tasks and a lot of JavaScript on the main thread.
| Metric | Measures | Core Web Vital? | Field or lab | “Good” per web.dev |
|---|---|---|---|---|
| LCP (Largest Contentful Paint) | Render time of the largest image, text block or video visible in the viewport, from the start of navigation | yes (loading) | field and lab | 2.5 s or less |
| INP (Interaction to Next Paint) | Latency of interactions across the whole visit until the next paint; one value that all (or nearly all) interactions fall below | yes (interactivity), since 2024-03-12 | field; in the lab only with simulated interactions, Lighthouse does not measure INP | 200 ms or less |
| CLS (Cumulative Layout Shift) | Largest burst of unexpected layout shifts during the entire lifecycle of the page | yes (visual stability) | field and lab | 0.1 or less |
| TTFB (Time to First Byte) | Time from the start of navigation until the first byte of the response arrives | no (helps diagnose LCP) | field and lab | 0.8 s or less |
| FCP (First Contentful Paint) | Time from the start of navigation until any part of the page's content is rendered | no (helps diagnose LCP) | field and lab | 1.8 s or less |
| TBT (Total Blocking Time) | Total time after FCP during which the main thread was blocked long enough to prevent input responsiveness | no (lab proxy for INP) | lab; web.dev does not recommend field measurement | less than 200 ms on average mobile hardware |
| Speed Index | How quickly content is visually displayed during page load (from a video of the load) | no | lab (Lighthouse) | Threshold according to Lighthouse: mobile up to 3.4 s “fast” (web.dev gives no value) |
| FID (First Input Delay), historical (this term) | Time from the first interaction until the browser can begin processing event handlers | until 2024-03-12, replaced by INP | field only | 100 ms or less |
According to web.dev, the 75th percentile of page loads is assessed, mobile and desktop separately. A page passes the Core Web Vitals when LCP, INP and CLS are “good” at the 75th percentile. Chrome tools ended FID support on September 9, 2024. Sources: web.dev: Web Vitals; web.dev: Largest Contentful Paint (LCP); web.dev: Interaction to Next Paint (INP); web.dev: Cumulative Layout Shift (CLS); web.dev: Time to First Byte (TTFB); web.dev: First Contentful Paint (FCP); web.dev: Total Blocking Time (TBT); web.dev: First Input Delay (FID); web.dev Blog: Interaction to Next Paint is officially a Core Web Vital (2024-03-12); Chrome for Developers: Lighthouse – Speed Index. Last checked: .
Sources
- First Input Delay (FID) – web.devweb.dev
- INP becomes a Core Web Vital on March 12 – web.devweb.dev
- First input delay – MDNdeveloper.mozilla.org
Last updated: