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To render custom HTML as an image or PDF, send the markup—and optionally CSS—to a rendering API, then request the output format you need. In the HTML/CSS to Image API, you can provide either HTML or a public webpage URL, with CSS optional; its documented formats include PNG, JPG, WebP, and PDF. Other services may use different endpoints, inputs, and layout rules.
What a HTML-to-image API does
A rendering API turns HTML into a visual file. You can send a snippet or complete document for rendering, or ask the service to capture a public webpage by URL. When sending markup, CSS can be supplied to control styling. This is useful for generating share cards, receipts, charts, reports, and other images or documents from application data.
The HTML/CSS to Image API is one provider-specific example, not a universal interface. Its documentation describes an authenticated POST request to https://hcti.io/v1/image, using JSON or form data. Provide either an html value or a url value; they are alternatives. CSS is optional and can also be injected when capturing a URL. The docs list the images:create permission for image creation.
Send HTML and choose an output
- Prepare the input. Use an HTML fragment or full document, or use a publicly accessible webpage URL. Include CSS if the result needs specific fonts, colors, spacing, or layout.
- Choose the output format. The HTML/CSS to Image API lists PNG, JPG, WebP, and PDF. PNG is its documented default; specify another format when you need one.
- Set capture options if needed. For webpage screenshots, its docs describe viewport dimensions, full-screen capture, CSS selectors, headers, media type, delay or readiness controls, and color scheme. These are controls, not a promise that every dynamic page will render identically.
- Make an authenticated POST request. Send the input and any supported options as JSON or form data to the provider’s endpoint. Follow its current API documentation for exact parameter names and authentication syntax.
- Check the returned file. Inspect dimensions, text, clipping, and layout before using the output in production, especially if the source page loads content dynamically.
PNG, WebP, JPG, or PDF?
| Format | Use it when | Consider |
|---|---|---|
| PNG | You want a raster image and the documented default is convenient. | Check the resulting dimensions and whether the image needs transparency. |
| JPG | You need a raster image in JPG format. | Verify that text and fine detail remain legible at the intended size. |
| WebP | You want a raster image in WebP format. | Confirm that the systems consuming the file support WebP. |
| You need a paginated document rather than a single raster image. | Check page size, breaks, margins, fonts, and print-versus-screen styling in the specific provider. |
PDF behavior is provider-specific. The HTML/CSS to Image API documentation lists PDF output and PDF options, but do not assume its pagination or CSS handling matches another service. As one separate example, html2img documents vector PDF output with selectable text and embedded fonts, A4 portrait pages with automatic pagination, and normal screen CSS rather than @media print rules. Those details apply to html2img as documented at its format parameter reference, not to every HTML rendering API. Test page breaks, typography, and margins with the service you choose.
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Protect the API key
The HTML/CSS to Image API advises treating an API key like a password: someone who obtains it may use operations allowed by its permissions. Its documentation recommends limiting a key to the operations the application needs. As a practical implementation measure, keep secret keys on your server rather than exposing them in public browser code or logs. See the provider’s API guidance.
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For a webpage screenshot rather than rendering arbitrary markup, ScreenshotNeo accepts one GET request with a URL and returns PNG, JPEG, WebP, or PDF. It removes cookie and consent banners, newsletter popups, and chat widgets before capture; bot checks, blank pages, failed loads, and cache hits are not billed. Its MCP server lets AI agents use screenshot tools, and the free plan includes 1,000 shots per month without a card; paid plans start at $5 for 3,000 shots.
For example, this cURL call captures a webpage as WebP:
curl -G "https://api.screenshotneo.com/v1/shot" -d access_key=YOUR_API_KEY --data-urlencode url=https://stripe.com -o shot.webpSee the ScreenshotNeo API documentation for options and authentication details. Sign up free for 1,000 screenshots a month, with no card required.
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