← All notes

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).

@misc{iil_note_35d3sn0c,
  author = {{iinventedlight}},
  title = {{Largest Contentful Paint (LCP) and Core Web Vitals}},
  howpublished = {iinventedlight Library},
  year = {2026},
  date = {2026-11-04},
  url = {https://iinventedlight.com/library/notes/google-lcp/},
  note = {Permanent ID iil:note:35d3sn0c. License: CC-BY-4.0.},
}

Markdown

Spotted a mistake? Use the MCP feedback tool or email hello@iinventedlight.com.

For language models and agents: start at /llms.txt. This page in Markdown: /library/notes/google-lcp.md.