Timing Charts: A Blueprint For SMIL Animations

The article walks readers through a practical workflow for building SMIL‑based SVG animations, starting with a simple color‑and‑opacity change that uses separate <animate> elements for each property. By assigning IDs such as colorChange and opacityChange and leveraging SMIL’s begin attribute with syncbase expressions like colorChange.end ‑ 300ms, the author demonstrates precise, relative timing without external scripts. The guide also highlights that modern browsers have supported SVG geometry properties natively since 2024, meaning attributes like fill and opacity can be animated directly in an <img> reference, while still respecting the prefers-reduced-motion media query—a requirement underscored by accessibility advocate Val Head.

In the wider front‑end ecosystem, SMIL sits between CSS keyframe animations and the newer Web Animations API (WAAPI). While CSS excels at animating a handful of properties and WAAPI offers JavaScript‑driven control, both struggle to animate every SVG attribute when the asset is embedded via <img>. SMIL fills that gap, but its one‑property‑per‑tag model has historically led to bloated markup, discouraging adoption. By introducing timing charts—a visual planning tool that maps start and end points on a line—the article gives designers a method to orchestrate multiple SMIL elements cleanly, mirroring how developers use Gantt charts for project timelines. This approach could revive interest in SMIL, especially for static‑site generators or CMS pipelines where inline JavaScript is undesirable.

Looking ahead, the technique’s viability hinges on continued browser support for SMIL syncbase offsets and the eventual addition of CSS‑equivalent properties for still‑unsupported SVG attributes like viewBox. If major browsers begin to deprecate SMIL in favor of WAAPI, teams that have invested in timing‑chart‑driven SMIL may face costly rewrites. Conversely, tooling that auto‑generates SMIL from timing charts could lower the barrier to entry and encourage broader use. Developers should monitor Chrome, Edge, and Safari release notes for any changes to SMIL parsing, and consider fallback strategies—such as providing a <picture> element with a static fallback—for environments where SMIL support wanes.