Account for visual effects
Large images, extra fonts, and simultaneous animations add loading and processing costs. Give each effect a purpose. Simplify it if it makes reading or interaction harder.
Prepare assets for their display size
Match image dimensions to their use and reserve layout space before loading. Load images further down the page when needed. Provide alternatives and reduced-motion behavior for video and demanding effects.
Check the main journeys
Test the menu, form, language switcher, and scrolling at different screen sizes. Assess whether people can complete their task comfortably. Looking good on one fast device is not enough.