Which AI assistants train on your chats?
The short answer
Of the nine assistants whose policies we read on 22 September 2026, ChatGPT, Gemini and Mistral Vibe train on your chats by default, and each lets you switch that off. Perplexity lists model training too, without a documented switch. Claude only trains if you opt in. Copilot in Microsoft 365, Duck.ai, Brave Leo and Proton Lumo do not train on them.
In detail
The table below sets out, per assistant, what happens to what you type, where the switch sits and what the cheapest paid plan costs. Privacy settings and prices were read on each provider's own pages on 22 September 2026, and every price is shown in the currency the provider displayed.
The switch matters most where training is on until you act. OpenAI sends you to its privacy portal, where you click "do not train on my content", or to Temporary Chat for a single conversation that stays out of training.
Gemini ties it to Gemini Apps Activity. Turn "Keep Activity" off and new chats are removed after 72 hours instead of 18 months. Google adds a catch of its own: chats a human reviewer has looked at can be kept for up to three years, even after you delete your activity.
For Vibe, the assistant Mistral used to call Le Chat, the help center gives two routes. On the web, open admin.mistral.ai, pick Vibe under Manage and turn off "Allow your interactions to be used to train our models". In the phone app, go to Settings, Data & Account Controls and turn off "Enable data sharing".
Two rows need a footnote. Perplexity's privacy policy names improving its AI models as a use of your data but describes no off switch, so there is no menu path to give. Microsoft's no-training promise covers Copilot inside Word, Excel and Outlook; the free Copilot app runs under a separate privacy page.
Do you not trust the switch? Then do not lean on it. A setting only covers chats from the moment you flip it, and an app update can move it. Whatever the policy says, keep account numbers, medical details, passwords and client files out of every chatbot.
The other route is a tool where training is off by design. Duck.ai is free, needs no account and has contracts that bar its model providers from training on your prompts. Brave says Leo stores no prompts or answers on its servers. Lumo encrypts saved chats so that Proton itself cannot read them.
Lumo also has a free plan. Lumo AI Plus costs €9.99 a month on the annual plan, billed as €119.88 a year, against €12.99 when you pay month to month. Claude stays a reasonable pick too, as long as the "Help Improve our AI models" switch under Settings, Privacy remains off.
What nine AI assistants do with your chats (read on 22 September 2026)
| Assistant | Trains on your chats by default | How to turn it off | How long chats are kept | Servers | Cheapest paid plan | Same currency, USD per month (ECB 2026-09-01) | Source |
|---|---|---|---|---|---|---|---|
| ChatGPT | Yes, unless you opt out | privacy.openai.com > "do not train on my content"; Temporary Chat for one conversation | Not stated | Not stated | Go: €8 a month | $9.27 | https://openai.com/policies/how-your-data-is-used-to-improve-model-performance/ |
| Claude | No, only if you opt in | Nothing to switch off; check your name > Settings > Privacy > "Help Improve our AI models" | Deleted chats leave the back end within 30 days; up to 5 years, de-identified, if you allow training | Not stated | Pro: €15 a month billed yearly, or €18 monthly | $20.86 | https://privacy.claude.com/en/articles/10023580-is-my-data-used-for-model-training |
| Gemini | Yes, while Keep Activity is on (the default) | myactivity.google.com/product/gemini > "Keep Activity" off | 18 months by default; 72 hours with Keep Activity off; chats seen by a reviewer up to 3 years | Not stated | Google AI Plus: €4.99 a month | $5.78 | https://support.google.com/gemini/answer/13594961 |
| Microsoft Copilot (in Microsoft 365 apps) | No | Nothing to switch off | Not stated | Not stated | Microsoft 365 Personal: $99.99 a year, or $9.99 a month | $9.99 | https://support.microsoft.com/en-us/privacy/copilot-in-microsoft-365-apps-for-home-your-data-and-privacy |
| Perplexity | Yes, according to its privacy policy | No switch described in the privacy policy | "Only as long as necessary", no fixed period | Not stated | Pro: $17 a month, billed yearly | $17 | https://www.perplexity.ai/hub/legal/privacy-policy |
| Duck.ai (DuckDuckGo) | No | Nothing to switch off | On your device; Sync & Backup removed after 18 months unused; model providers delete within 30 days | DuckDuckGo cloud providers, region not stated | Plus: $99.99 a year, or $9.99 a month | $9.99 | https://duckduckgo.com/duckai/privacy-terms |
| Brave Leo | No | Nothing to switch off; local history under brave://settings/leo-ai | Not stored on Brave servers; large prompts cached for minutes | Not stated | Leo AI premium: $14.99 a month, or $149.99 a year | $14.99 | https://brave.com/privacy/browser/ |
| Mistral Vibe (formerly Le Chat) | Yes, unless you opt out | admin.mistral.ai > Manage > Vibe > Privacy > "Allow your interactions to be used to train our models" off; app: Settings > Data & Account Controls > "Enable data sharing" off | No period stated for chats | EU by default, optional US endpoint | Pro: $14.99 a month, excluding tax | $14.99 | https://help.mistral.ai/en/articles/455207-can-i-opt-out-of-my-input-or-output-data-being-used-for-training |
| Lumo (Proton) | No | Nothing to switch off | Not stated; saved chats are zero-access encrypted | Europe, on servers Proton controls | Lumo AI Plus: €9.99 a month billed yearly, or €12.99 monthly | $15.06 | https://proton.me/support/lumo-privacy |