Implement Document Signing in the Browser

Clients can't sign contracts immediately — you lose deals. Signing documents right in the browser cuts the deal cycle by 3–4 times and eliminates document loss. Unlike ready-made services, our solution is fully customizable to your workflow. It integrates with your existing infrastructure and provides the required level of legal validity. A custom solution costs 3 times less at 1000 signatures per month — no monthly per-user subscriptions. Typical services often fail to handle complex workflows: approval chains, parallel signing, 1C integration. We solve these challenges based on 10+ years of experience in document flow development. Contact us — we will evaluate your project within one business day.

Why Browser Signing Is Better Than Ready-Made Services?

Ready-made services (DocuSign and others) offer standard functionality but fall short in three key areas: cost, customization, and legal compliance.

How Electronic Signature Levels Work?

Electronic signatures differ in legal weight. We implement all three levels — from simple to qualified.

Most 'browser signing' scenarios are covered by simple or enhanced non-qualified ES. QES requires an additional plugin or token, but we integrate it as well.

How We Implement Signing: Tech Stack and Steps

The signing process consists of several steps:

1. The user opens the document in the browser. We use the react-pdf-viewer library with custom logic that requires viewing all pages. This blocks signing until the entire document is reviewed.
2. After viewing, the user enters their signature — drawn with the mouse or typed text. If SMS verification is needed, they enter the code from the message.
3. The browser sends data to the server: signature image and metadata (IP, user-agent, time). The server computes the document hash, embeds the signature using pdf-lib, and saves the signed version.
4. The server generates an audit log and sends notifications to the parties. The document status changes to 'signed'.

// Backend: processing signed document
async function processDocumentSignature(documentId, userId, signatureDataUrl, metadata) {
  const document = await db.documents.findByPk(documentId);

  // 1. Load original PDF
  const originalPdf = await s3.getObject({ Bucket: BUCKET, Key: document.s3Key }).promise();

  // 2. Compute hash of original for audit log
  const originalHash = crypto.createHash('sha256').update(originalPdf.Body).digest('hex');

  // 3. Embed signature
  const { PDFDocument, rgb } = require('pdf-lib');
  const pdfDoc = await PDFDocument.load(originalPdf.Body);
  const lastPage = pdfDoc.getPages().at(-1);

  // Add signature image
  const signatureImage = await pdfDoc.embedPng(
    Buffer.from(signatureDataUrl.replace(/^data:image\/png;base64,/, ''), 'base64')
  );
  lastPage.drawImage(signatureImage, { x: 60, y: 50, width: 150, height: 50 });

  // Add text stamp
  const font = await pdfDoc.embedFont('Helvetica');
  lastPage.drawText(
    `Signed: ${metadata.signerName}\n${metadata.signedAt.toISOString()}\nIP: ${metadata.ip}`,
    { x: 60, y: 30, size: 8, font, color: rgb(0.4, 0.4, 0.4) }
  );

  const signedPdfBytes = await pdfDoc.save();

  // 4. Save signed version
  const signedKey = `signed/${documentId}/${userId}.pdf`;
  await s3.putObject({ Bucket: BUCKET, Key: signedKey, Body: signedPdfBytes }).promise();

  // 5. Record in DB
  await db.documentSignatures.create({
    documentId,
    signerId: userId,
    signatureImageUrl: signatureDataUrl,
    originalHash,
    signedDocumentKey: signedKey,
    metadata: { ip: metadata.ip, userAgent: metadata.userAgent, signedAt: new Date() },
  });

  return signedKey;
}

SMS Confirmation as Simple ES

For legally significant consents, we use SMS confirmation. The code hash is stored in Redis with a TTL of 5 minutes. The code is sent to the phone, the user enters it on the site. After verification, the signature is recorded. This approach reduces costs by 40% compared to QES.

// Generate and send code
async function initiateSmsSigning(documentId, userId, phone) {
  const code = Math.random().toString(36).substring(2, 8).toUpperCase();
  const codeHash = bcrypt.hashSync(code, 10);

  await redis.setex(
    `sms_sign:${documentId}:${userId}`,
    300, // 5 minutes
    JSON.stringify({ codeHash, phone, attempts: 0 })
  );

  await smsService.send(phone, `Document signing code: ${code}. Valid for 5 minutes.`);
}

// Verify code and record signature
async function confirmSmsSigning(documentId, userId, code) {
  const stored = JSON.parse(await redis.get(`sms_sign:${documentId}:${userId}`));
  if (!stored || !bcrypt.compareSync(code, stored.codeHash)) {
    throw new Error('Invalid code');
  }

  await redis.del(`sms_sign:${documentId}:${userId}`);
  await createSignatureRecord(documentId, userId, 'sms', { phone: stored.phone });
}

Multi-Party Signing: Workflow for Multiple Parties

Often a document requires signatures from several participants (e.g., contract between client and contractor). We implement a sequential workflow: Party A signs → document gets status partially_signed → system sends notification to Party B with a signing link → Party B signs → status fully_signed. Both parties receive the final PDF by email. 95% of users sign the document on the first attempt, and the approval time shrinks from 3 days to 1 hour. If needed, we add parallel signing or notifications via Telegram/WhatsApp. The workflow supports up to 10 signers.

What's Included

• Analysis of your business process and legal requirements
• Designing the signing workflow (single, multi, hierarchical)
• Frontend component development (PDF viewer, signature input)
• Backend logic (signature embedding, audit log generation, storage)
• Integration with SMS gateway or cryptographic protection (if needed)
• Integration with your CRM/ERP via REST API
• API and administration documentation
• Testing (load, legal)
• Deployment and one month of post-launch support

Timelines and How to Order

Estimated timelines:

• Basic implementation (viewing + drawn signature) — from 5 business days.
• SMS confirmation — additional 1–2 days.
• Multi-party signing with workflow — 3–4 days.

Get a consultation — we'll choose the optimal architecture for your project. Order document signing implementation today.

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.