Rendertron

Why deploy Rendertron on Render?

Rendertron is a headless Chrome rendering service that serializes JavaScript-rendered web pages into static HTML. It solves the problem of search engine bots and crawlers that cannot execute JavaScript, allowing Progressive Web Apps and SPAs to serve pre-rendered content for SEO and social sharing purposes.

This template gives you a production-ready Rendertron instance with Puppeteer and headless Chrome already configured—no wrestling with Chrome dependencies, Dockerfile setup, or memory tuning for serverless environments. Render's one-click deploy handles the tricky parts of running headless browsers (which notoriously break on other platforms due to missing system dependencies), so you can start improving your PWA's SEO immediately. You skip the hours typically spent debugging Chrome sandbox issues and container configuration.

What you can build

You'll have a headless Chrome rendering service that can pre-render your JavaScript-heavy pages on demand. Point bots and crawlers at it via middleware so they receive fully-rendered HTML instead of an empty shell, making your SPA or PWA indexable by search engines that don't execute JavaScript.

Key features

• Headless Chrome Rendering: Uses Puppeteer to render JavaScript-heavy pages and serialize the fully-rendered HTML for bots and crawlers.
• Auto-detect Page Load: Automatically detects when a page has finished loading by monitoring the page load event and outstanding network requests.
• Screenshot API: Provides GET/POST endpoints to capture page screenshots with configurable viewport dimensions and mobile emulation.
• Express.js Middleware: Includes middleware for differential serving that checks user agents to determine when to proxy requests to the rendering service.
• Configurable Timeout Budget: Supports a 10-second rendering budget with customizable timeout settings via config.json for controlling render duration.

Use cases

• SEO engineer prerenders JavaScript-heavy PWA pages for search engine crawlers
• Developer debugs rendering issues by capturing screenshots of client-side apps
• DevOps team serves static HTML to social media bots for link previews
• Agency verifies web component sites render correctly for non-JS clients

Next steps

1. Test the render endpoint by visiting your-service-url/render/https://example.com — You should see the fully rendered HTML of example.com returned as plain text within 10 seconds
2. Take a screenshot by navigating to your-service-url/screenshot/https://example.com — You should see a JPEG image of the example.com homepage displayed in your browser
3. Configure your PWA's middleware to proxy bot requests to your Rendertron URL — You should see search engine bots receiving fully rendered HTML when you check your server logs or test with a user-agent switcher

Resources

• Rendertron official site