Web app development is the design and build of software that runs in the browser, such as customer portals, booking systems, dashboards and SaaS products. Devsinn builds web apps for UK businesses in Next.js and React with fixed-scope pricing in GBP, weekly demos, accessibility and security built in, and full code ownership.
What you get
Fast on every device
Pages that load quickly on mobile data, not just office Wi-Fi.
Easy for users
Clear journeys designed and tested with real people.
Secure by default
Authentication, roles and encryption built in from day one.
Found on Google
Technical SEO and Core Web Vitals handled properly.
What is the difference between a website and a web app?
A website mainly presents information. A web app lets users do things: log in, book, pay, upload files, manage accounts or see live data. Web apps need user accounts, databases, permissions and integrations, so they are built more like software than a brochure site, with testing and security to match.
Customer and partner portals with secure logins.
Booking, quoting and ordering systems.
Internal dashboards and admin panels.
SaaS products with subscriptions and billing.
How much does a web app cost in the UK?
A focused web app with a few core features typically starts from £12,000 + VAT. A customer portal with integrations usually starts from £18,000 + VAT, and a SaaS product with billing and admin from £25,000 + VAT. We fix the price for the first version after discovery and phase the rest.
Indicative web app costs (GBP, + VAT)
Type
Typical price
Typical timeline
Focused web app (core features)
From £12,000
6 to 8 weeks
Customer portal with integrations
From £18,000
8 to 12 weeks
SaaS product with billing and admin
From £25,000
10 to 14 weeks
Hosting, monitoring and support
From £400 a month
Ongoing
Why do you build with Next.js?
Next.js is a widely used React framework backed by Vercel. It gives fast page loads, strong SEO, a secure server layer and a large hiring pool, so your app is easy to maintain and extend later. For most UK business web apps it balances speed of build, performance and long-term cost very well.
Server rendering for speed and search visibility.
One codebase for the public site and the logged-in app.
Deploys to Vercel, AWS or Azure with UK or EU regions.
How do you make web apps accessible and secure?
We design to WCAG 2.2 AA, test with keyboard and screen readers, and check colour contrast. On security, we follow OWASP guidance: proper authentication, role-based access, input validation, encrypted data, dependency scanning and least-privilege cloud access. Security and accessibility are part of the acceptance tests, not an afterthought.
Can you add AI features to our web app?
Yes. Common additions are an assistant that answers questions from your own content, smart search, document summarisation, form auto-fill and automated triage. We add them where they save users time, keep personal data under control, and measure whether they are actually used.
How it works
Free 20-minute call
Your users, goals and what the first version must do.
Discovery and design
User journeys, clickable prototype, scope and a fixed price.
Build
Sprints with weekly demos on a staging site you can click through.
Launch
Performance, accessibility and security checks, then go live.
Support
Hosting, monitoring, updates and the next features in priority order.
What it costs
Indicative prices in GBP, excluding VAT. We fix the price in writing after a short scoping call. Full price guide
Focused web app
From £12,000+ VAT
International: From $15,300
Design and prototype
Core features and logins
Testing and launch
Portal or SaaS
From £18,000+ VAT
International: From $23,000
Integrations
Roles and admin panel
Billing where needed
Support and hosting
From £400+ VAT
per month
International: From $510
Uptime monitoring
Security updates
Monthly improvements
A good fit if you
Businesses giving customers or partners self-service online
Founders launching a SaaS product in the UK
Teams replacing slow, dated internal web systems
Not the right fit if you
A simple brochure website (a template is cheaper)
Projects needing a live product in under two weeks
Briefs without anyone to review weekly demos
Questions people ask
Still unsure? Ask us on a free 20-minute call.
How long does it take to build a web app?
A focused web app usually takes six to eight weeks after discovery. Portals with integrations take eight to twelve weeks, and SaaS products with billing ten to fourteen. We release a usable first version early and add features in planned phases, so you see value sooner.
Will our web app work on mobile phones?
Yes. Every web app we build is responsive and tested on common phones, tablets and browsers. If you later need app store presence, offline use or device features like push notifications and the camera, we can add a mobile app that shares the same back end.
Who owns the web app once it is built?
You do. The code, designs and content are assigned to you on payment, and the repository and hosting accounts sit in your name. You can host it anywhere, hire any developer to extend it, or bring it in-house without needing our involvement.
Where is our data hosted?
We default to UK or EU regions on AWS, Azure, Google Cloud or Vercel, chosen to suit your UK GDPR needs and budget. We document where each type of data lives and who can access it, and we can meet specific hosting requirements from your sector or customers.
Can you redesign or rebuild an existing web app?
Yes. We start with a short review of the current app, its code and its users, then recommend whether to improve it in place or rebuild in stages. Staged rebuilds keep the old system running until each part is replaced, so your customers are not disrupted.
Do you handle SEO for web apps?
We handle technical SEO: fast Core Web Vitals, clean URLs, metadata, structured data, sitemaps and accessible markup. That gives public pages the best chance to rank. Ongoing content and link building are separate, and we can recommend specialists if you need them.
What does it cost to run a web app?
Hosting and services for a typical business web app cost tens to a few hundred pounds a month, depending on traffic and data. Our optional support plan from £400 + VAT a month covers monitoring, updates, backups and small improvements.
