cubic-bezier.com

Lea Verou's bezier curve editor: drag the handles, compare against presets, share via URL

Tier A · StrongToolReferencecubic-bezier.com

cubic-bezier.com is a single-purpose editor for CSS timing functions. You drag the two control points of a cubic-bezier curve, preview the motion at an adjustable duration, and compare your curve side by side against the CSS defaults and a saved library of presets. The curve is encoded in the URL fragment (for example cubic-bezier.com/#.17,.67,.83,.67), so any curve is a permalink you can paste into a ticket or a code review. Built by Lea Verou, MIT-licensed, and effectively finished — it has not needed to change in years.

For an agent

You cannot read a curve out of this page — it is a canvas app — but you can write one into it: construct https://cubic-bezier.com/#x1,y1,x2,y2 and hand that link to the human when you want them to approve or nudge an easing you chose. Reach for easings.net first to pick a named curve, then link here only when the answer is 'close, but slower at the end'. Four values in a URL is also a good way to record a design decision in a PR description.

Why it is here. It is the canonical shared workspace for the one CSS function nobody can read by eye, and the URL-encoded curve makes motion decisions reviewable. Twelve years old, still the first link anyone sends.

Install command, framework, licence and component list.

Facts

License: MIT
Pricing: Free, Open source
Framework: Vanilla JS
Styling: Vanilla CSS
Distribution: Web app / online tool, GitHub repository
Platform: Web
Content type: Code
Agent readiness: Copy-paste ready code, Readable open source, Client-rendered shell
Accessibility: Not applicable
Maturity: Stable
GitHub stars: 184

Components it ships

Transition Animation

Notable for

curve encoded in the URL fragment
side-by-side comparison against presets
adjustable-duration live preview
MIT, by Lea Verou
no build, no account, no tracking wall

Provenance

Verified 2026-08-16. HTTP 200. https://cubic-bezier.com (WebFetch + curl 200), https://github.com/LeaVerou/cubic-bezier (WebFetch), https://api.github.com/repos/LeaVerou/cubic-bezier (184 stars, MIT, pushed 2024-07-15)

Also in Utilities & Naming

cubic-bezier.comTier A