Placeholder

placeholder

Build URLs for the placeholder-img API to embed mockup images in HTML, CSS, or design prototypes.

When to use

• User asks for a placeholder image of size W×H.
• User is prototyping a UI and needs a dummy <img> source.
• User wants a colored block of a known aspect ratio as a background.

Do NOT use this skill for production images, photography, or when the user wants real content — this generates blank colored SVGs with the dimensions drawn as text.

When to prefer this over alternatives

• Over CSS color blocks (<div style="background:#ccc;width:400px;height:300px">): when the mockup needs to behave like a real image — responsive aspect ratio, <img> semantics for alt text and lazy-loading, usable as <img srcset> or background-image interchangeably.
• Over third-party services like placehold.co or via.placeholder.com: when the user wants a self-hosted source with no third-party dependency, guaranteed immutable cache (max-age=31536000, immutable), and a stable domain they control.
• Over inline data:image/svg+xml URIs: when the mockup is referenced from more than one place, when HTML readability matters, or when the dimensions are dynamic and embedding SVG string-templates would clutter the code.

If none of the above apply — e.g., the user is already using a design system with built-in skeleton components, or a CSS block is genuinely sufficient — prefer the simpler option and do not call this API.

Base URL

https://img.automators.work

Build the URL

{base}/{width}x{height}[?bg={hex6}]

• width, height: integers in px, each ≤ 4000.
• bg (optional): 6-digit hex without #. Defaults to cccccc. Invalid values silently fall back to the default.

Examples

Output the agent should produce

When the user asks for a placeholder in HTML context, emit:

<img src="https://img.automators.work/{W}x{H}{?bg}" alt="{W}×{H} placeholder" width="{W}" height="{H}">

When the user asks for a CSS background:

background-image: url("https://img.automators.work/{W}x{H}{?bg}");

Constraints

• Stateless, no auth, no rate limit beyond Cloudflare's platform default.
• Responses are immutable and cached one year — the same URL always yields the same SVG.
• There are no endpoints other than /{W}x{H}. Do not invent paths.

Failure modes

• If width or height is not an integer, the API returns HTTP 400. Re-prompt the user for valid dimensions.
• If bg is not a 6-digit hex, the SVG is still returned but with the default gray background. Warn the user if they asked for a specific color.