@rdub/og-lambda

Scheduled AWS Lambda for generating og:image screenshots. Takes a screenshot of a URL on a schedule and uploads it to S3.

Installation

pnpm add @rdub/og-lambda

Usage

Config file

Create .og-lambda.json in your project:

{
  "stackName": "myproject-og",
  "screenshotUrl": "https://mysite.com",
  "s3Bucket": "my-bucket",
  "s3Key": "og-image.jpg"
}

Then deploy:

og-lambda deploy
og-lambda status
og-lambda config   # Show resolved configuration

Environment variables override config file values.

Configuration options

Config key	Env var	Default	Description
screenshotUrl	SCREENSHOT_URL	(required)	URL to screenshot
s3Bucket	S3_BUCKET	(required)	S3 bucket for output
s3Key	S3_KEY	og-image.jpg	S3 key (path) for output
stackName	STACK_NAME	og-lambda	CloudFormation stack name
viewportWidth	VIEWPORT_WIDTH	1200	Screenshot width
viewportHeight	VIEWPORT_HEIGHT	630	Screenshot height
waitForSelector	WAIT_FOR_SELECTOR	-	CSS selector to wait for
waitForFunction	WAIT_FOR_FUNCTION	-	JS expression that must return truthy
waitForTimeout	WAIT_FOR_TIMEOUT	-	Extra ms to wait after load
quality	SCREENSHOT_QUALITY	90	JPEG quality (0-100)
scheduleRateMinutes	SCHEDULE_RATE_MINUTES	60	How often to run
timezone	TIMEZONE	-	Timezone for page rendering

CDK-only options (env vars):

Env var	Default	Description
LAMBDA_MEMORY	2048	Lambda memory in MB
LAMBDA_TIMEOUT_MINUTES	2	Lambda timeout

Using the screenshot function directly

import { takeScreenshot } from '@rdub/og-lambda'

const { buffer, contentType } = await takeScreenshot({
  url: 'https://example.com',
  width: 1200,
  height: 630,
})

How it works

1. EventBridge triggers the Lambda on a schedule (default: hourly)
2. Lambda launches headless Chrome via @sparticuz/chromium
3. Takes a screenshot of the configured URL
4. Uploads the JPEG to S3 with public caching headers
5. Your site's <meta property="og:image"> points to the S3 URL

Requirements

• Node.js 20+
• AWS CDK CLI (npm install -g aws-cdk)
• AWS credentials configured
• S3 bucket with appropriate permissions

Architecture

EventBridge (hourly) → Lambda → Puppeteer/Chrome → S3 bucket
                                                      ↓
                        Your site ← og:image URL ← Public URL

Examples

• awair.runsascoded.com – Hourly screenshots of air quality charts with Plotly.js, using waitForFunction to wait for chart rendering (config, og:image)

Development

pnpm install
pnpm build        # Compile TypeScript
pnpm package      # Bundle for Lambda
pnpm synth        # Preview CloudFormation
pnpm deploy       # Deploy to AWS