How does aspect-ratio handling work?

Pass only resizeWidth (or only resizeHeight) and Rendex scales the other dimension to preserve the original aspect ratio. Pass both to fit within that bounding box without distorting the image.

Can I upscale a screenshot to make it larger?

No. Resize only downscales. If your requested size is larger than the captured image, Rendex returns the image at its captured size rather than enlarging it, so you never get a blurry, stretched result.

Which output formats can be resized?

Image formats — PNG, JPEG, and WebP. PDF output is not resized; for smaller PDFs use the pdfScale and pdfFormat options instead.

Is resize available on the GET endpoint?

Yes. resizeWidth and resizeHeight are supported on both POST /v1/screenshot and GET /v1/screenshot, so you can embed a downscaled capture directly in an URL. It's available on every plan, including Free.

Use Case

Capture Full-Resolution, Ship a Right-Sized Thumbnail

Add resizeWidth (and optionally resizeHeight) and Rendex downscales the rendered image before it returns — preserving aspect ratio, never upscaling. Generate gallery thumbnails, link previews, and responsive image sets from a single render call.

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The Problem

A full-page or retina screenshot is great for detail and terrible for a thumbnail grid — multi-megabyte PNGs blow up page weight and bandwidth. The usual fix is a second pipeline: pull the full image, run it through a resizing library or an image CDN, store the variants, and keep them in sync. That's a lot of moving parts for 'make it smaller.'

The Solution

Rendex resizes the output for you. Pass resizeWidth and/or resizeHeight and the rendered PNG, JPEG, or WebP is downscaled server-side before the response — aspect ratio preserved when you give only one dimension, and never enlarged past the captured size. It works on both POST /v1/screenshot and the GET endpoint, so you can build <img> thumbnail URLs directly. (Resize applies to images; PDF output isn't resized.)

See it in action

A page rendered at 1280 by 800 on the left and the same image downscaled to 640 by 400 with resizeWidth on the right.

Get Started in Minutes

thumbnail.sh

# resizeWidth works on the GET endpoint too — perfect for <img> thumbnail URLs
curl -s -H "Authorization: Bearer YOUR_API_KEY" \
  "https://api.rendex.dev/v1/screenshot?url=https://example.com&resizeWidth=320" \
  -o thumb.png

thumbnail.js

import Rendex from "@copperline/rendex";
import { writeFileSync } from "fs";

const rendex = new Rendex("YOUR_API_KEY");

// Render at full size, get a 320px-wide thumbnail back.
const thumb = await rendex.screenshot({
  url: "https://example.com",
  resizeWidth: 320,
});

writeFileSync("thumb.png", thumb.image);

thumbnail.py

from rendex import Rendex
from pathlib import Path

rendex = Rendex("YOUR_API_KEY")

# Aspect-preserving downscale to a 320px-wide thumbnail.
thumb = rendex.screenshot(url="https://example.com", resize_width=320)
Path("thumb.png").write_bytes(thumb.image)

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Built for This Use Case

One-Parameter Downscale

resizeWidth and resizeHeight (16–3840 / 16–2160 px) downscale the rendered image server-side before it returns — no second request, no extra service.

Aspect-Preserving

Give only one dimension and Rendex keeps the original aspect ratio, scaling the other to match — so thumbnails never look stretched or squashed.

Never Upscales

Resize only ever shrinks. If your target is larger than the captured image, Rendex returns it at the captured size — no blurry upscaling artifacts.

Works on GET <img> URLs

resizeWidth and resizeHeight are query params on GET /v1/screenshot, so you can point an <img src> straight at a right-sized capture with no code.

Pairs with Any Capture

Combine resize with fullPage, device presets, dark mode, or HTML/Markdown input. Render once and downscale — a clean fit for responsive image sets.

Free on Every Plan

Output resize is available on every plan, including Free, and adds no extra call — it's a parameter on the render you're already making.

Start Free, Scale as You Grow

100 calls/month free. Starter at $69/mo for 10K calls (or $58/mo billed annually — 2 months free). Pro at $179/mo for 100K calls.