🔒 On-device · Data never leavesDeft
A privacy-first Chrome extension that fills signup forms in one click, keeping personal data on the device.
- Role
- Sole developer, from architecture through to Chrome Web Store release
- Period
- 2026
Overview
A privacy-first Chrome extension (Manifest V3) that fills signup forms in one click. A deterministic mapper reads each form's labels and attributes locally, and only unrecognised fields go to a model, either Chrome's on-device Gemini Nano or a cloud model via OpenRouter. Personal data never leaves the device: the model returns a field-to-key mapping, and the substitution happens in the page. Zero dependencies, no build step, with a shadow-DOM review panel and framework-safe value setting.
How it's built
Deterministic mapping first
A local mapper reads each form's labels, names and attributes and resolves the fields it recognises without any model call. Only genuinely unrecognised fields are escalated.
Personal data never leaves the device
The model receives field descriptors and returns a field-to-key mapping, never the user's values. Substitution happens in the page, so stored personal data is never transmitted.
On-device or cloud inference
Unrecognised fields resolve through Chrome's built-in Gemini Nano via the Prompt API where available, falling back to a cloud model through OpenRouter.
Zero dependencies, no build step
Written as plain ES modules against Chrome Manifest V3, with a Shadow DOM review panel that cannot be styled by the host page and framework-safe value setting for React and Vue forms.
Technology stack
- Chrome MV3
- Vanilla JS (ES Modules)
- Gemini Nano (Prompt API)
- OpenRouter
- Shadow DOM
- chrome.storage
- Node Test Runner
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Building something similar?
I'm Hazem Elsawy, a Full Stack Developer in Perth, WA. If this is the kind of work you need, I'd like to hear about it.