A feature-rich browser extension that lets you read, compose, and manage your Proton Mail right from the toolbar — without ever opening a tab.
*.proton.meClassic, Modern and Material UI themes, plus a range of color and layout themes — each in light, dark or auto. The gallery shows whichever matches this page; flip the toggle to see the rest.
Click any theme to view it full-size · ← → to browse
Here’s what the extension stores, and where. All traffic goes to Proton’s servers except for hCaptcha (during human verification) and a small license-check endpoint for Pro subscriptions. No analytics, no telemetry.
Security boundary. The encryption key for the at-rest secrets is stored in the same browser-storage area, so this protects against casual profile inspection and accidental exposure in backups, but not against malicious browser extensions or a compromised user profile. If that’s in your threat model, Proton Mail in a private browser profile with only vetted extensions is the stronger choice.
Want stricter isolation? If you’d rather have no Proton data touching local extension storage — or any other link in the chain — use Proton Mail’s web interface directly, which keeps everything in the tab session only. You give up popup convenience in exchange for zero additional trust.
Proton Mail is excellent in a tab. Mail Checker is for the times you’d rather not keep one open.
| Capability | Mail Checker | Proton Mail web app | Bridge + email client |
|---|---|---|---|
| Read & reply from the browser toolbar | Yes | NoIt is a full browser tab | NoUses a separate desktop email client |
| New-mail notifications without a Proton Mail tab open | YesBackground polling on your chosen interval | NoPer Proton’s docs, the web app notifies while a tab is open | Via your email client |
| Works on a free Proton plan | YesFree tier; Pro is optional | Yes | NoBridge needs a paid Proton Mail plan |
| What you install | A browser extension | Nothing — a browser tab | A desktop app + an email client |
| End-to-end encrypted (OpenPGP) | Yes | Yes | Yes |
Proton’s first-party options, as of June 2026. Proton Mail Bridge runs on paid Proton Mail plans and provides IMAP/SMTP to desktop email clients.
Use the free version indefinitely or upgrade to Pro for the full experience.
€0
Includes a 14-day Pro trial — try every feature first
€2.38
per month, or €26.18 / year · incl. German VAT (other countries may differ)
One subscription is for a single person. For team, family or business use, contact me. Payments processed by Paddle.com, our Merchant of Record.
No. As of 2026, Proton offers no official browser extension for Proton Mail — its Mail clients are the web app, the mobile and desktop apps, and Proton Mail Bridge (IMAP/SMTP for desktop email clients, on paid plans). Proton Pass and Proton VPN do have official extensions, but those aren’t for Mail. Mail Checker for Proton Mail is an independent extension and is not affiliated with Proton AG.
Mail Checker lives in your browser toolbar. It signs in to your account directly using Proton’s SRP login and checks for new mail in the background, so you can read, reply and compose from the popup without opening mail.proton.me in a tab.
Proton’s web app shows new-mail desktop notifications while Proton Mail is open in a browser tab (per Proton’s support docs); for other cases Proton points to its mobile apps and email notifications. Mail Checker is built for exactly this gap — it polls in the background on an interval you choose and shows desktop notifications without a Proton Mail tab open. More on Proton Mail notifications in the browser →
Yes. Mail Checker monitors several Proton Mail accounts at the same time, each with its own folders, labels, colour and notification settings. (The free tier covers a single account; multiple accounts are part of Pro.)
It signs in with Proton’s SRP protocol, so your password never leaves your device. Its browser host access is limited to *.proton.me and it talks only to Proton’s servers — the only exceptions are hCaptcha during Proton’s human-verification step and a small licence check for Pro subscriptions. There is no analytics and no telemetry. The Data & Encryption section above lists exactly what is stored and where.
Proton Mail Bridge is a desktop app — available on paid Proton Mail plans — that runs a local IMAP/SMTP server so you can use a separate email client such as Thunderbird or Outlook. Mail Checker is a browser extension with its own popup, needs no separate client, and has a free tier. They solve different problems.
Replies are personal — no ticketing systems, no chatbots.
Please include the extension version (Settings → About) and your Firefox or Chrome version when reporting bugs.
A native Android sync adapter for Proton Contacts and Proton Calendar — fully encrypted, works with every app on your phone.