Wall & Fifth
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Web App Development Agency — London

Software that
lives in the browser.
Not a brochure.

Wall & Fifth designs and engineers custom web applications, SaaS products, marketplaces, portals and operational platforms. Next.js, React, TypeScript and PostgreSQL. Fixed-price builds from £16,000, with full code ownership.

Production web application
Interface
Next.js · React · TypeScript
Application
Auth · roles · workflows · business logic
Data
PostgreSQL · APIs · integrations
Infrastructure
Deployment · environments · monitoring

Web application development

A web app is software.
The browser is just where it runs.

Accounts & access

Authentication, sessions, user roles and permissions.

Application UI

Dashboards, workflows, tools and stateful interfaces.

Persistent data

Structured application data and business logic.

Backend systems

APIs, integrations, jobs and operational services.

What we build

Different products.
Same production discipline.

SaaS applications

Subscriptions, accounts, billing, permissions, dashboards and product workflows.

Marketplaces

Multiple user groups, listings, search, enquiries, transactions and operational tooling.

Customer portals

Secure self-service environments around accounts, documents, payments and workflows.

Internal platforms

Operational tools, admin systems, dashboards and software replacing manual processes.

AI-enabled products

Applications where AI capabilities are integrated into a wider product and data architecture.

The stack

Modern web engineering,
without unnecessary complexity.

Next.js
Application framework

Routing, rendering, server capabilities and production delivery.

React
Interface layer

Reusable product interfaces and interactive application state.

TypeScript
Application code

Typed frontend and backend logic that is easier to maintain.

PostgreSQL
Data layer

Relational application data, queries and persistent product state.

These are typical technologies rather than a rulebook. The architecture should follow the product, integrations and operational requirements.

Web or mobile?

Start where the product
benefits most.

A web app is often stronger when

Users need instant access with no install
Desktop usage matters
Links and sharing matter
Search visibility matters
The product changes frequently
One application needs to work across many devices

Mobile becomes stronger when

Usage is frequent and on the move
Push notifications are central
Camera, location or device capabilities matter
Home-screen presence changes behaviour
The product needs a deeply mobile interaction model
Mobile app development

Beyond the interface

The parts users
do not see.

Authentication & permissions
Accounts, sessions, recovery and role-based access structured around the product.
Database & data modelling
Application data structured for the actual relationships, workflows and reporting needs of the product.
APIs & integrations
Payments, communications, external systems, data providers and specialist services connected into the application.
Admin & operations
The internal interfaces needed to manage users, content, transactions, support and exceptions.
Performance
Rendering, caching, database access and application behaviour treated as production concerns.
Deployment & handover
Production environments, source repository and application ownership handed over rather than locked behind a proprietary platform.

Pricing

Scope the system.
Fix the price.

Focused web applicationfrom £16,000

A defined production application with the core users, workflows, data and integrations required for launch.

Extensive web applicationfrom £30,000

A larger system with more user types, deeper workflows, admin tooling, integrations or operational complexity.

Read the app development cost guide

Common questions

Before you build the application.

Wall & Fifth is a London-based product and software development studio building custom web applications, SaaS products, marketplaces, portals and operational platforms. Work covers product strategy, UX/UI, frontend, backend, integrations, testing and production deployment.

A website primarily presents information. A web application lets users perform actions and stores application state: accounts, dashboards, workflows, transactions, permissions, data and other interactive functionality.

Wall & Fifth typically builds web applications with Next.js, React and TypeScript, with PostgreSQL and suitable backend services or APIs behind them. The architecture is chosen around the product rather than a fixed template.

Focused web application builds start from £16,000. Larger systems with multiple user roles, complex workflows, admin tooling or substantial integrations typically start from £30,000.

A web application is often the stronger first choice when accessibility, sharing, search visibility, desktop use or zero-install access matter. Native mobile becomes more valuable when frequent on-the-go usage, notifications or device capabilities are central to the product.

Yes. Web applications can include registration, login, sessions, password recovery, permissions and role-based access appropriate to the product.

Yes. Wall & Fifth builds integrations with payment providers, external APIs, data services, AI services and other third-party platforms where required by the product.

Yes. The finished codebase and associated intellectual property are handed over to the client. There is no proprietary app-builder platform or software licensing lock-in.

Related software expertise

Explore the product architecture around the web app.

App DevelopmentMobile App DevelopmentCross-Platform AppsReact Native DevelopmentApp Development CostApp Development for StartupsSaaS DevelopmentMarketplace DevelopmentAI App Development

Build the system,
not just the screens.

Tell us what users need to do, what data the product needs to hold, and what systems it needs to connect to.

Book a scoping call