placeholders.dev

Generate super-fast placeholder images in 330+ edge locations, powered by Cloudflare Workers

Info

placeholders.dev generates custom placeholder images on the fly, such as the examples above. All of these images are generated on Cloudflare's Edge, at 330+ locations, ensuring the best possible performance for all of your users. All images are cached for lengthy periods of time.

Technology

This project makes use of Cloudflare Workers, and Cloudflare Workers Static Assets. It also implements a HTMLRewriter to update the total Cloudflare PoPs in multiple locations.

Example URLs:

• Basic url path: https://images.placeholders.dev/350
• Full url path: https://images.placeholders.dev/350x150
• Full query params:https://images.placeholders.dev/?width=1055&height=100&text=Made%20with%20placeholders.dev&bgColor=%23f7f6f6&textColor=%236d6e71

Available API Options

• width
  • Width of generated image. Defaults to 300.
• height
  • Height of generated image. Defaults to 150.
• text
  • Text to display on generated image. Defaults to the image dimensions.
• fontFamily
  • Font to use for the text. Defaults to sans-serif.
• fontWeight
  • Font weight to use for the text. Defaults to bold.
• fontSize
  • Font size to use for the text. Defaults to 20% of the shortest image dimension, rounded down.
• dy
  • Adjustment applied to the dy attribute of the text element to appear vertically centered. Defaults to 35% of the font size.
• bgColor
  • Background color of the image. Defaults to #ddd
• textColor
  • Color of the text. For transparency, use an rgba or hsla value. Defaults to rgba(0,0,0,0.5)
• textWrap
  • Wrap text to fit within the image (to best ability). Will not alter font size, so especially long strings may still appear outside of the image. Defaults to false.

WebMCP

While placeholders.dev is open, it registers tools with the visitor's AI agent via the draft WebMCP navigator.modelContext API, so an agent can build placeholder URLs from a plain-language request without any setup. Tools live in public/webmcp.js and are pure URL work, so no requests leave the browser.

• generate_placeholder_image_url
  • Builds a validated image URL from any of the API options above, and returns HTML and Markdown snippets alongside it. Values the image API would silently drop, such as an unparseable color or a fontWeight keyword, are rejected with an explanation instead. Also renders the result on the page so the visitor can see what the agent produced.
• explain_placeholder_image_url
  • Breaks an existing placeholders.dev URL into the options it uses, resolves the defaults the image API would apply, and flags query parameters it ignores.

Dev

• npm run start:dev (this will use wrangler dev to locally start the Cloudflare Worker for testing)

or

• npm run publish (push to placeholders-dev workers.dev)

or

• npm run publish:staging (push to placeholders-staging workers.dev)

Production

• npm run publish:prod (publishes to placeholders.dev via Workers)