The browser extension boundary is mobile browser social sessions, not native app composers. Safari iOS and Firefox Android should be evaluated separately because their extension behavior and maintenance costs differ from desktop Chrome.
Technical spec
Mobile browser extension technical spec
A mobile browser extension technical spec for Safari iOS and Firefox Android should come after mobile web, Android keyboard, and iOS keyboard plus Share Extension validation. It should serve browser-first social reply users, use visible page context with clear permission copy, keep copy fallback available, and avoid pretending to solve native app composer workflows.
Last updated: July 11, 2026. This page is written for implementation-intent SEO and AI citation.
System boundary
What does this spec own?
Data flow
How should context and drafts move?
Detect browser session
The user is replying from a mobile browser page rather than a native social app composer.
Capture visible context
The extension reads or transfers the visible post context needed to draft a useful reply after user action.
Generate drafts
The same TypeToSell reply API returns platform-aware drafts under account and quota rules.
Copy or insert
The extension copies or inserts selected text only where browser capability allows, with mobile web fallback always available.
Permission model
What access must stay explicit?
Page access explanation
Permission copy should name the visible-page context job instead of asking for broad trust.
Browser-specific scope
Safari iOS and Firefox Android permissions should be documented separately because assumptions do not transfer cleanly.
Fallback first
Mobile web share/copy should remain available when browser APIs or page structure block insertion.
No native app claim
Public pages should not describe browser extensions as solving native X, Reddit, or Facebook app composers.
Instrumentation
What must be measured?
Browser-first usage
Measure users who reply from mobile browser sessions before prioritizing extension work.
Context capture success
Track whether visible page context can be captured accurately enough for useful drafts.
Copy fallback rate
Measure how often extension users need copy fallback instead of insertion.
Maintenance signal
Track browser-specific breakage or review friction before expanding support.
Failure modes
What can go wrong, and how should it be prevented?
Wrong segment
The extension is built for users who actually reply in native apps.
Require browser-first usage evidence before prioritization.
Desktop assumptions
The spec copies Chrome desktop behavior into mobile Safari or Firefox.
Evaluate each mobile browser separately before promising capture, insertion, or fallback behavior.
Capability overpromise
Copy implies universal insertion across mobile social apps.
State browser limits and keep copy fallback visible.
Rollout gates
What must be true before rollout?
Gate 1
Browser-first segment is real
Research or analytics shows meaningful Safari iOS or Firefox Android browser-based replying.
Gate 2
Context feasibility is proven
Visible page context can be captured or transferred without excessive permission overreach.
Gate 3
Fallback path works
Selected copy and mobile web fallback remain usable when insertion is limited.
Gate 4
Support cost is justified
QA, review, and browser-specific maintenance are justified by the segment size.
Related reading
Continue from specs to execution
Browser extension requirements/requirements/mobile-browser-extension-requirementsBrowser extension checklist/checklists/safari-ios-firefox-android-extension-checklistBrowser extension matrix/matrices/mobile-browser-extension-priority-matrixMobile browser examples/examples/mobile-browser-extension-reply-examples
FAQ
Technical spec questions
What is a mobile browser extension technical spec?
It defines context capture, permission scope, selected copy or insertion, fallback behavior, and maintenance gates for mobile browser social replying.
Do mobile browser extensions replace ReplyPilot Keyboard?
No. Browser extensions help mobile browser pages, while keyboards help native mobile app composers.
Should mobile browser extensions ship first?
No. They should come after the mobile web MVP and after evidence shows browser-first replying is meaningful.