---
source: https://iinventedlight.com/library/notes/google-lcp.md
title: "Largest Contentful Paint (LCP) and Core Web Vitals"
license: CC-BY-4.0
license_url: https://creativecommons.org/licenses/by/4.0/
source_license: "CC BY 4.0 (web.dev live page footer: 'the content of this page is licensed under the Creative Commons Attribution 4.0 License'; cite the page, not the archived repo); prose restated in our own words; footer re-checked live 2026-11-05"
license_family: web.dev
rule_check: "needs rule check (family not in auto-publish rule; check.mjs auto-approves only usgov and arxiv-ccby)"
attribution: "Summary by iinventedlight (AI-assisted). Sources: Google (web.dev), Largest Contentful Paint (LCP)  |  Articles  |  web.dev, CC BY 4.0 (web.dev live page footer: 'the content of this page is licensed under the Creative Commons Attribution 4.0 License'; cite the page, not the archived repo); Google (web.dev), Web Vitals  |  Articles  |  web.dev, CC BY 4.0 (web.dev live page footer: 'the content of this page is licensed under the Creative Commons Attribution 4.0 License'; cite the page, not the archived repo)."
author: "iinventedlight (synthesis of cited sources); text drafted with AI assistance"
date: 2026-11-04
status: published
checked_on: 2026-11-05
as_of: 2026-11-05
confidence: medium
untested: "No code was run for this note; only the fetched documentation pages were read."
category: coding-references
topic_area: "code-ai-eng: web performance"
tags: ['web-performance', 'core-web-vitals', 'lcp']
sources:
  - id: S1
    title: "Largest Contentful Paint (LCP)  |  Articles  |  web.dev"
    publisher: Google (web.dev)
    url: https://web.dev/articles/lcp
    accessed: 2026-11-05
    license: "CC BY 4.0 (web.dev live page footer: 'the content of this page is licensed under the Creative Commons Attribution 4.0 License'; cite the page, not the archived repo)"
  - id: S2
    title: "Web Vitals  |  Articles  |  web.dev"
    publisher: Google (web.dev)
    url: https://web.dev/articles/vitals
    accessed: 2026-11-05
    license: "CC BY 4.0 (web.dev live page footer: 'the content of this page is licensed under the Creative Commons Attribution 4.0 License'; cite the page, not the archived repo)"
---
# Largest Contentful Paint (LCP) and Core Web Vitals

**Answer:** LCP is the time, counted from the start of navigation, until the largest image, text block, or video in the viewport has rendered. Aim for 2.5 seconds or less. (S1)

## Why a new metric

- Measuring when a page's main content becomes visible has long been hard for developers. (S1)
- Older signals such as `load` or `DOMContentLoaded` fire at moments that may not match what the user actually sees. (S1)
- First Contentful Paint (FCP) is user-centric but only marks the very start of loading. (S1)
- Judge the 2.5-second target at the 75th percentile of page loads, splitting mobile and desktop. (S1)

## Core Web Vitals context

- Web Vitals is Google's effort to give one consistent set of guidance on the quality signals that shape user experience. (S2)
- Core Web Vitals are the subset that applies to every web page; every site owner should measure them, and Google tools report them. (S2)
- The set of Core Web Vitals metrics is expected to change over time. (S2)
- LCP sits alongside INP (good at 200 ms or less) and CLS in the current set. (S2)

## Claims
- id: C1
  claim: A good LCP is 2.5 seconds or less.
  source: S1
  evidence: "A good LCP value is 2.5 seconds or less."
- id: C2
  claim: Measure at the 75th percentile of page loads.
  source: S1
  evidence: "a good threshold to measure is the 75th percentile of page loads"
- id: C3
  claim: Core Web Vitals will evolve over time.
  source: S2
  evidence: "The metrics that make up Core Web Vitals will evolve over time."
- id: C4
  claim: Good INP is 200 ms or less.
  source: S2
  evidence: "pages should have a INP of 200 milliseconds or less."

## Sources
- [S1] Largest Contentful Paint (LCP)  |  Articles  |  web.dev. Google (web.dev). https://web.dev/articles/lcp . License: CC BY 4.0 (web.dev live page footer: 'the content of this page is licensed under the Creative Commons Attribution 4.0 License'; cite the page, not the archived repo). Accessed 2026-11-05.
- [S2] Web Vitals  |  Articles  |  web.dev. Google (web.dev). https://web.dev/articles/vitals . License: CC BY 4.0 (web.dev live page footer: 'the content of this page is licensed under the Creative Commons Attribution 4.0 License'; cite the page, not the archived repo). Accessed 2026-11-05.

License: this note is CC BY 4.0 (https://creativecommons.org/licenses/by/4.0/). Summary by iinventedlight (AI-assisted).