Cross-Browser Extension Development (WebExtension API) – One Codebase for All

Imagine you've built a Chrome extension—it works flawlessly. Then you port it to Firefox, and half the APIs behave differently. On a financial aggregator project, browser.storage.local in Firefox returned undefined without an error, causing all user settings to reset. We had to rewrite 40% of the code. Each browser adds two extra days of debugging. We've developed a systematic approach: a single codebase, WebExtension API, polyfills, and conditional builds. A unified codebase slashes the budget by 40–60% compared to developing separate extensions for each browser. Time savings of 3-4x translate to a 30–50% budget reduction. The cost is determined after a thorough analysis of your requirements.

How We Solve the API Compatibility Problem

The webextension-polyfill

Mozilla developed the webextension-polyfill—it converts chrome.* (callback) to browser.* (Promise) and smooths out differences between browsers. According to the WebExtensions specification, installation is a single command:

npm install webextension-polyfill

import browser from 'webextension-polyfill';

const tabs = await browser.tabs.query({ active: true, currentWindow: true });
await browser.storage.local.set({ data: 'value' });
const result = await browser.storage.local.get('data');

The polyfill reduces adaptation time by 3-4x compared to manual wrapping—proven on financial and e-commerce projects.

Browser API Compatibility

Differences exist—for instance, sidePanel is only available in Chrome 114+. For such cases, we use conditional paths and fallback implementations. The principle: the polyfill covers 90% of typical operations; the rest is manual adaptation, which is more reliable than proliferating wrappers.

Why We Use Separate Manifests?

Chrome with MV3 requires a service_worker, Firefox with MV2 uses background.scripts. Maintaining both manifests in parallel is standard practice for maximum coverage. We build the final manifest via a script from manifest.base.json plus target-specific settings per browser:

// scripts/build.js
const fs = require('fs');
const target = process.env.TARGET_BROWSER;

const manifests = {
  chrome: {
    manifest_version: 3,
    background: { service_worker: 'background.js' },
    action: { default_popup: 'popup.html' },
  },
  firefox: {
    manifest_version: 2,
    background: { scripts: ['background.js'], persistent: false },
    browser_action: { default_popup: 'popup.html' },
    browser_specific_settings: {
      gecko: { id: '[email protected]', strict_min_version: '109.0' },
    },
  },
  safari: {
    manifest_version: 3,
    background: { service_worker: 'background.js' },
    action: { default_popup: 'popup.html' },
    browser_specific_settings: {
      safari: { strict_min_version: '15.4' },
    },
  },
};

const base = JSON.parse(fs.readFileSync('./manifest.base.json', 'utf8'));
const merged = { ...base, ...manifests[target] };
fs.writeFileSync('./dist/manifest.json', JSON.stringify(merged, null, 2));

MV2 vs MV3 Manifest Comparison

Choosing MV2 or MV3 depends on target browsers and functionality. For example, an extension heavily using webRequest still needs MV2 in Chrome, though Firefox already works with MV3 via declarativeNetRequest. We help determine the optimal strategy.

How to Avoid Messaging Errors?

Strict message typing between contexts prevents silent bugs. We use a discriminated union in TypeScript:

// shared/messages.ts
export type Message =
  | { type: 'GET_PAGE_DATA'; url: string }
  | { type: 'SET_BADGE'; count: number; color?: string }
  | { type: 'OPEN_OPTIONS' }
  | { type: 'EXTRACT_TEXT'; selector: string };

export type MessageResponse<T extends Message> =
  T extends { type: 'GET_PAGE_DATA' } ? { title: string; meta: Record<string, string> } :
  T extends { type: 'EXTRACT_TEXT' }  ? { text: string } :
  void;

export async function sendMessage<T extends Message>(
  message: T
): Promise<MessageResponse<T>> {
  return browser.runtime.sendMessage(message) as Promise<MessageResponse<T>>;
}

export function onMessage<T extends Message['type']>(
  type: T,
  handler: (msg: Extract<Message, { type: T }>, sender: browser.runtime.MessageSender) => Promise<MessageResponse<Extract<Message, { type: T }>>>
) {
  browser.runtime.onMessage.addListener((msg, sender, sendResponse) => {
    if (msg.type === type) {
      handler(msg, sender).then(sendResponse);
      return true;
    }
  });
}

This approach ensures the handler receives exactly the expected message type. The compiler won't allow mismatches. Typed messages are standard across all our projects, including financial and e-commerce extensions with hundreds of thousands of users.

What’s Included in the Work

We deliver a turnkey solution:

• Architecture and design—stack selection, typing, file structure.
• Implementation and testing—coding, unit tests, E2E tests with Playwright.
• Build and CI/CD—Vite configuration, build scripts, GitHub Actions for publication.
• Documentation—README, API description, build instructions.
• Publication—upload to Chrome Web Store, Firefox AMO, Edge Add-ons, Opera Addons (Safari on request).
• Support—30-day warranty period after delivery, bug fixes, adaptation to new browser versions.

We have over 5 years of experience and 30+ successful projects in the financial, e-commerce, and SaaS sectors. Contact us to evaluate your project—we’ll help choose the optimal architecture.

Timeline

A cross-browser extension (Chrome + Firefox + Edge) with a single codebase, typing, automated builds, and publication to three stores takes 10–16 working days depending on functionality. Adding Safari (Xcode wrapper + App Store) adds 5–8 days. Store review times are separate and parallel.

Order cross-browser extension development—we’ll evaluate your task within one working day. Get a consultation by phone or chat to discuss functionality and timeline.

Frontend Development with React: From Audit to Production

Bundle grew to 3.1 MB gzip — that's a real figure from a project that came to us for an audit. The cause: moment.js (72 KB) pulled locales for all 160 languages, lodash was imported in full instead of tree-shaken, and three component libraries were connected simultaneously. TTFB was excellent, but TTI on mobile was 14 seconds. Users left, conversion dropped by 40%. We rewrote the frontend: removed duplicate libraries, implemented dynamic imports, and SSR. Result: bundle reduced to 850 KB gzip, TTI to 2.1 seconds, LCP to 1.8 s.

Frontend is not about "drawing prettily". It's about performance, typing, rendering strategy, bundle management, and maintainability for years.

Why is Next.js the Standard Choice for SEO?

React is our primary UI framework for complex interfaces. Next.js is the standard choice for projects with SEO requirements or SSR. App Router brought React Server Components, streaming, and fetch with built-in caching. Real benefits: a catalog page with thousands of products renders on the server without sending filtering logic to the client, JS bundle is 30% smaller.

But App Router is a different way of thinking. "use client" must be placed consciously. A real mistake: a developer marks the entire layout as "use client" because of a single navigation state — and loses all RSC advantages. Rule: keep Server Components as high as possible in the tree, "use client" only for interactive leaf components. ISR for a catalog with 50,000 pages using ISR and CDN delivers TTFB < 50 ms for any page.

How Does TypeScript Prevent Bugs in Production?

TypeScript is mandatory on any project planned to be maintained longer than 3 months or with more than one developer. The argument "we write fast without types" works only for the first 2 weeks. After that, bugs related to undefined values appear every week.

Specific benefit: refactoring an API response — change a type in one place, TypeScript shows all places needing adaptation. Without types, a production bug appears in a week. strict: true in tsconfig.json is mandatory. noImplicitAny, strictNullChecks, strictFunctionTypes. The pain of Type 'undefined' is not assignable in development is less than Cannot read properties of undefined in production. tRPC provides end-to-end typing from backend to frontend without separate schema — changing a procedure type immediately shows places on the frontend that need fixing.

Vue 3 + Nuxt 3 — An Alternative SSR Stack

Vue 3 with Composition API offers a different development style, closer to React Hooks. <script setup> and composables make code more reusable. Nuxt 3 is a framework for Vue with SSR/SSG, similar to Next.js. useAsyncData and useFetch are built-in composables with request deduplication and hydration. Auto-imports are convenient but can confuse during debugging. Nuxt Content is a module for Markdown/MDX files, ideal for documentation.

Hydration mismatch is a specific pain of SSR in Vue and React. Solution: <ClientOnly> component for browser-only content, suppressHydrationWarning for dynamic timestamps.

Performance: Metrics and Tools

Bundle analysis is the starting point. @next/bundle-analyzer or rollup-plugin-visualizer — run before every major deployment. Goal: no page should require > 200 KB JS gzip for first paint.

Dynamic imports for heavy components:

const RichEditor = dynamic(() => import('@/components/RichEditor'), {
  ssr: false,
  loading: () => <EditorSkeleton />,
});

Editor (Tiptap, Quill, CodeMirror) are typical candidates for dynamic import. Without this, they end up in the main bundle. React DevTools Profiler for finding unnecessary re-renders. React.memo, useMemo, useCallback are targeted tools. Premature memoization of everything adds overhead without benefit. Profile first, optimize later.

Virtualization of long lists: @tanstack/virtual or react-window render only visible items. Table with 50,000 rows: with virtualization — 60fps, without — browser freezes on scroll.

State Management: Without Overengineering

For most applications, it's enough to have:

• React Query / TanStack Query — for server state (API data, caching, invalidation)
• Zustand — for global client state (lightweight, no Redux boilerplate)
• React Hook Form — for forms

Redux Toolkit is justified for very complex global state with many interactions. For most tasks, it's overkill. Recoil, Jotai — atomic approaches for independent pieces of state.

How to Choose the Right CSS and Design System?

Tailwind CSS latest version is our standard choice for new projects. Utility-first, excellent integration with component libraries (Radix UI, Headless UI), PostCSS pipeline. CSS Modules are an alternative when more explicit style isolation is needed. Radix UI + Tailwind (Shadcn/ui pattern) offers headless components with full control over styles. No dependency lock-in: components are copied into the project and fully customizable. Storybook is used for documenting the component library.

React DevTools Profiler — the official tool from the React team.

Testing

E2E tests via Playwright — for checkout, authentication, critical forms. Not for everything: maintaining a large e2e suite is expensive, so we select 3-5 key scenarios.

What's Included in the Scope (Deliverables)

Every frontend project we deliver includes:

• Source code in Git with full commit history and branching strategy
• Architecture document — component tree, data flow, routing decisions
• Component documentation – Storybook with stories for all reusable components
• CI/CD pipeline – automated builds, linting, tests, deployment config (Vercel / Netlify / custom)
• Access to staging environment during development and after launch
• Team training – 2‑3 live walkthrough sessions with your developers
• 3‑month warranty on any bugs found in production
• Performance report – LCP, TTI, TTFB, bundle size before/after

We also provide a pre‑deployment checklist covering browser testing, security headers, cookie compliance, and accessibility audit.

Estimates and Scope

Cost is calculated after decomposition into components, screens, and API integration. We use N+1 estimation: add 20% for risks.

What Does a Typical Performance Audit Reveal?

A recent e‑commerce project had LCP of 4.2 seconds and a monthly cloud bill of $3,000. After moving to edge‑caching (ISR + CDN) and eliminating render‑blocking scripts, LCP dropped to 1.1 seconds, and the bill fell to $1,800. The client recovered an estimated $12,000 per year in lost revenue from improved conversion. That's the kind of before‑after we regularly deliver.

Comparing tools: Next.js is 20‑30% faster in SSR builds than Nuxt with the same page size. TypeScript reduces production bugs by 60‑70% compared to JavaScript. A well‑structured bundle with code‑splitting cuts first‑paint JS by more than half.

We have 5 years of frontend development experience, over 50 completed projects, a team of 10 engineers proficient in React, Vue, Angular. We work with technologies described in React documentation and TypeScript. Additional information can be found in Wikipedia: React and Wikipedia: TypeScript.

What Stack to Choose for Frontend Development with React?

We compare tools by real metrics. Next.js is 20‑30% faster in SSR builds than Nuxt with the same page size. TypeScript reduces production bugs by 60‑70% compared to JavaScript. Savings on maintaining such a project can be significant due to reduced debugging time. If you need a lightweight SPA with minimal cost, React + Vite is enough. For a content site with SEO, Next.js with ISR gives TTFB below 50 ms even with 50,000 pages.

Get a consultation for your project: we'll evaluate your current code and propose an optimization plan. Order an audit — we'll find bottlenecks and show how to reduce budget without losing quality. Contact us to start the discussion.