Mozilla's opposition to Chrome's Prompt API

Context and Proposal

• Discussion centers on Chrome’s proposed Prompt API, which exposes local or cloud LLMs to websites via a standardized web API.
• Some see this as a natural next step, analogous to existing non-deterministic APIs (speech, geolocation); others see it as scope creep and unnecessary for the web.

Mozilla’s Objections

• Main technical concern: prompts quickly become tuned to a specific model’s quirks, breaking interoperability across browsers and future model versions.
• Worry that this creates “quirks-compat” with Google’s model, similar to past problems (IE, WebSQL/sqlite).
• Criticism of Chrome tying API usage to a “prohibited uses” policy that restricts content (e.g., sexual content, political misinformation) as inappropriate for a neutral browser API.

Interoperability and Model Lock-In

• Fear that sites will optimize for Gemini (or another dominant model) and effectively require Chrome, marginalizing other browsers and national/“sovereign” browsers without comparable models.
• Some argue exposing model identity or version is necessary for developers; others argue that would increase fingerprinting and lock-in.

Privacy, Fingerprinting, and Resource Costs

• Concerns that local models add powerful new fingerprinting vectors and can become de facto “device verification.”
• Local LLMs demand large downloads, disk space, and RAM/VRAM; users on modest hardware may see slowdowns and battery drain.
• Some see local models as a privacy win vs. cloud APIs; others ask why browsers should run LLMs at all instead of letting sites call remote APIs explicitly.

Security and Abuse Risks

• Worries about “LLM botnets”: malicious pages using the API for unconsented compute (similar to cryptomining).
• Prompt injection and expanded attack surface are seen as inevitable; calls for strict permissions and sandboxing, though some doubt this can be done confidently.

User Demand and “AI Everywhere” Skepticism

• Repeated pushback that “browsers and OSes are expected to gain LLMs” reflects vendor and shareholder expectations, not clear user demand.
• Many anecdotes of users turning off Copilot/AI features and distrusting AI-infused platforms, especially for sensitive tasks.

Alternatives and Standards Process

• Suggestions: keep AI support low-level (WebGPU-style), or use libraries like WebLLM rather than standardizing a high-level prompt API now.
• Some see this as another example of Google using Chrome’s dominance (after FLoC, Privacy Sandbox, WEI) to push self-serving standards; others say early shipping plus iteration is how web standards often mature.
• Broader frustration about browser monoculture, DRM, attestation, and lack of truly user-controlled browsers underpins the debate.