Parallax
Parallax is the effect in which layers move at different speeds as the page scrolls, creating a sense of depth.
Also known as: parallax scrolling · depth effect
The background moves slowly, the foreground quickly; the eye reads the difference as distance. It borrows from how the world looks from a moving train.
It was overused for years and became a cliché, which is why it is worth being precise: parallax works when it separates layers that genuinely belong at different depths. Applied to everything on the page it just makes reading harder.
When to use it
When it makes sense
When you want to give one section depth — a hero image, a product shot, a scene change.
When it is unnecessary
On a page of continuous text. Moving the background under a paragraph someone is reading is a distraction.
Common questions
Does parallax work on a phone?
It does, but with care: scroll is faster, the screen is smaller, and heavy parallax on mobile is a common source of stutter. It is often better to reduce or drop it on small screens.
Does it harm SEO?
Not in itself. It harms you if the text only appears after the movement — then the crawler may not see it. The content must be in the HTML regardless of the effect.
How does this term apply to your work? Let us talk.
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