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Firefox Relay vs 33Mail: catalog facts
Firefox Relay	33Mail
Freemium Free tier with a limited number of masks, paid plan for unlimited masks and a custom…	Free Free for unlimited aliases on the 33mail subdomain.
Web, Browser extension	Web
Backed by Mozilla, a long-standing name in browser privacy Simple mask creation directly from the browser	Unlimited free aliases on the service's subdomain Simple to create a new alias on demand for any signup
Free tier limits the number of masks available Deeper integration is tied to the Firefox browser ecosystem	Aliases live on 33mail's shared subdomain rather than a custom domain on the free tier Long-running service with a dated interface compared to newer alternatives
Web application, Browser extension	Web application
Closed source	Closed source
License not stated	License not stated
Not stated if an account is needed	Not stated if an account is needed
Not stated if it works offline	Not stated if it works offline
Official website Full listing and sources Checked September 22, 2026	Official website Full listing and sources Checked September 22, 2026

Catalog facts only. Anything “not stated” is unconfirmed. Check full listings for details.