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ChatGPT vs Lumo by Proton

Two fact sheets from our own research, side by side — pricing, platforms, API access and status re-checked by us rather than quoted from the vendors. ChatGPT starts at $8, Lumo by Proton at $9.99. Both have a free tier. Only ChatGPT ships a public API.

ChatGPTGeneral assistant with tools, memory, files and voiceLumo by ProtonA privacy-focused AI chat assistant from Proton with zero-access encryption on conversations.

Side by side

FactChatGPTLumo by Proton
CategoryGeneral-purpose AI ChatbotsGeneral-purpose AI Chatbots
Pricing modelFreemiumFreemium
Starts at$8 month$9.99 month
Public APIYesNo
PlatformsWeb, iOS, Android, macOS, Windows, APIWeb, iOS, Android
CompanyOpenAIProton AG
Launched2022—
Last verifiedSep 6, 2026Sep 1, 2026

What our research says

ChatGPT

ChatGPT is the default general assistant and the one everyone else is measured against, but the tier you need is rarely the one you first buy. Free is now ad-supported, and the jump to genuinely unlimited reasoning is steep.

Pros

  • Broadest tool surface of any consumer assistant: browsing, code, images, voice, connectors
  • The $8 Go tier closed the gap between free and a $20 commitment
  • Apps on every desktop and mobile platform, not just a web wrapper
  • Model quality is consistently at or near the front of the field

Cons

  • Advertising now appears on the free and Go tiers
  • Message and reasoning limits are opaque and change without notice
  • Tier structure has churned repeatedly, so any price you quote ages fast
  • The API is a separate purchase, which surprises buyers who assume Plus includes it

Lumo by Proton

Lumo's differentiator is genuinely structural rather than a marketing claim: Proton AG built its reputation on zero-access encrypted email and applies the same model here, plus a Tor option for account-free use. The free plan's limits on history and image generation are tight enough that regular users will likely need Plus fairly quickly.

Pros

  • Zero-access encryption is a real architectural claim backed by Proton's existing email/VPN business, not new marketing copy
  • Guest access over Tor works without any account at all
  • Available on web, iOS, and Android rather than browser-only

Cons

  • Free plan caps message history, image generation, and projects tightly enough to push regular users to Plus
  • Annual billing ($9.99/mo) is meaningfully cheaper than the $12.99 monthly rate, which isn't obvious until checkout

Which one fits

Choose ChatGPT if you need

  • General knowledge work, drafting, analysis and code across one interface
  • Anyone who wants file, image, voice and browsing input without assembling tools
  • Teams that need admin controls and data-retention terms via Business or Enterprise
  • Light users who want more headroom than free without paying $20

Choose Lumo by Proton if you need

  • Users who already trust Proton's privacy model and want an AI chat under the same guarantees
  • Anyone wanting to try AI chat anonymously via Tor without creating an account

More comparisons

All ChatGPT alternatives →Browse all General-purpose AI Chatbots →