ReSmush.it vs Screenshotlayer

ReSmush.it is a free, keyless image-optimization API — best known as the backend behind the ReSmush.it WordPress plugin — that accepts a source image URL and returns a JSON payload with the compressed image's URL plus original size, compressed size, and percent reduction. A live call against api.resmush.it needed no credentials and returned Access-Control-Allow-Origin: *, so it works directly from browser JavaScript. The plain http:// endpoint immediately redirects to https, so the service is https-only despite requiring no API key.

Screenshotlayer (an APILayer product) is a REST API that renders any public URL into a PNG, JPEG, GIF, or WebP screenshot, with parameters for viewport size, full-page capture, and retina/2x scaling. A live GET against api.screenshotlayer.com/api/capture with a bogus access_key returns a 101 invalid_access_key JSON error rather than serving anonymously, proving every call requires a real key passed as the access_key query parameter — auth is corrected from "None" to "API Key". That same probe carried Access-Control-Allow-Origin: * even on the error response, resolving the stored "unknown" cors to "yes". screenshotlayer.com/pricing lists a Free plan alongside paid Basic/Professional/Business tiers billed annually — freemium.