Private Mode, Public Servers
Every browser but Firefox now curbs AI in private windows. Almost none of them says so.
We ran current builds of all seven major AI-enabled browsers, plus Opera’s agentic Neon, hands-on, on 27, 28, and 29 July 2026. This report traces where data flows when a private window is open, which flows reach the frontier AI labs, what each vendor documents, and what we observed that no vendor has written down.
Download the report (PDF)12 pages · free · no signup required
Edition of 29 July 2026 · last revised 29 July 2026
The lockout is now the norm.
Chrome, Brave, and Opera disable their page-reading assistants in private windows and document it. Comet excludes its Assistant on the current build. We verified each of these in the running products. The lockouts cover the assistant, never the search box.
Firefox is the last unguarded path from a private page to a frontier lab.
Firefox's sidebar offers Claude, ChatGPT, Gemini, Mistral, or Copilot. The shipping code packages selected text, page excerpt, tab title, and URL, and contains no private-browsing check. The data goes to the chosen provider under that provider's retention rules.
Safari refuses to summarize private pages, and calls it an error.
The same article summarized in a normal window and was refused in a private window with "something went wrong," on two Apple Intelligence-enabled Macs. Apple presents a privacy behavior as a transient fault and documents it nowhere.
Edge shows you an AI button that does nothing.
In an InPrivate window, Edge's reader mode offers Summarize, Explain, and Chat with Copilot. Clicking Summarize produces no summary, no error, and no notice that the feature is unavailable there. Safari does the same thing with a misleading error message. Two vendors, two dead controls, zero documentation.
Products changed faster than the paperwork.
Comet's Assistant now shuts off in Incognito, and only the Incognito screen says so. Three vendors added private-window protection in silence this year. Protection nobody wrote down can revert the same way it arrived.
The search pipe stays open in every private window.
Chrome's Incognito address bar offers Google's AI Mode. A query typed in an Edge InPrivate window returns an answer labeled "Copilot Search" — the same brand name as the assistant Microsoft withholds from that window. Locking out the assistant does not close the search channel, and no private-mode screen mentions the AI sitting behind it.
Findings rest on vendor documentation, shipping product code, court records, and hands-on runs of current macOS builds: Chrome 150.0.7871.187, Edge 150.0.4078.105, Firefox 153.0, Brave 149.1.91.175, Opera 133.0, Opera Neon 133.0, Comet 150.0.7871.228, and Safari 26.5. Safari’s test was a same-page comparison on two Apple Intelligence-enabled Macs. Every product claim in the report is dated and versioned. Corrections: info@q16pbc.com.
Q16 Frontier Watch rates the privacy of consumer AI apps, traced through the hosting layer to the model provider behind each one. Browse the ratings.
28 July 2026 — first edition. Seven browsers, plus Opera Neon, tested hands-on.
29 July 2026 — Edge revised. The first edition reported Copilot absent from InPrivate, having checked only the toolbar and new-tab page. Further testing found its AI controls present in reader mode and inert when clicked, and Copilot-branded AI answering searches in the same window. The Chrome section was clarified to distinguish the Gemini assistant from AI Mode, a separate search product built on the same models.
We revise this report in place when further testing changes a finding, and we record what changed.
The Q16 newsletter carries new assessments, rating changes, and what moved at the frontier. No spam, unsubscribe anytime.