Separate measurement families
Core Web Vitals address main-content loading, responsiveness and visual stability. Record device, connection, cache and page version. Repeated measurements on a fast browser do not represent every reader. Field data, when available, supplements laboratory diagnosis.
Remove obstacles to reading
Reserve image dimensions and avoid inserting a late banner above text already on screen. Reduce work that blocks the main thread. Load essential first-screen imagery promptly, then defer suitable offscreen illustrations. Decorative motion should never prevent navigation, reading or interaction.
Compare consistent conditions
Test the homepage, articles, categories and tools on mobile and wide screens. Replay search, disclosure controls and calculator input. Inspect errors and horizontal overflow. A visual improvement must be observed in a rendered page rather than inferred from a CSS rule.
- Conditions
- Measurement
- Change
- Replay
Worked example
An image measuring 1,600 × 900 pixels can reserve its aspect ratio before loading. Text below it then retains its position. Compare measured layout shifts before and after under the same conditions.
Check before moving on
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Sources & method
Sources reviewed on 1 October 2026. Worked calculations use explicitly hypothetical inputs.
Topic provenance: Testez le temps de chargement de vos pages (2007-06-18). Search Engine Feng Shui. Byline retained in the consulted version: François Houste.
This guide is newly written in 2026. It does not reproduce the earlier text and is not attributed to its historical author.