We are big on creating eminently successful businesses - 🖥 products we have developed from scratch so far have raised in excess of 💰$495,000,000 in funding!
🙅♂️ No one failed projects
In addition, we were named as 👨🔬 "Best & innovative development company on the market" (c) RBC
Plus, we became🏅"Top #2 Web Development Company in the world" (c) Manifesto
Under-the-hood:
- ⏳ 11+ years on the global markets (🇺🇸, 🇬🇧, 🇻🇬, Asia, Eastern & Western Europe)
- 🗞 Publications in TechCrunch, Forbes, Business Insider, NY Times, Wired
- 🏪 HQ in London and plans for 🗺 New York and San-Francisco during next year
- 🚀 90+ unparalleled projects we are proud of
- 🏂 80+ developers, you can leverage (most of them are seniors)
- 🧗♀️ Own awesome Startup Competitions in London in partnerships with WeWork, Barclays, F6S, 11FS, Capital Enterprise, VCs
Focus Areas
Service Focus
- Web Development
- Mobile App Development
- Software Development
Client Focus
- Medium Business
- Small Business
- Large Business
Industry Focus
- Financial & Payments
- Education
- Healthcare & Medical
4xxi Executive Interview

95% of our customers are repetitive and recommend us to others.
We advice leveraging only on native development (for high-end products). Hybrid development does not allow using all the features of the OS, and requires native development for the functionalities that the hybrid platform does not provide.
The payment structure could be presented as Time & Material, Team-Based, Phases-based with monthly invoicing and so on. To be honest, it doesn`t matter a lot.
Commerce and Retail - e.g., Warby Parker
Transactional Services - e.g., Uber
Subscriptions - e.g. Salesforce
Marketplace - e.g., Etsy
Usage Fee - e.g., T-Mobile pre-paid
Service fee per unit - e.g., most of the Development agencies
Rental or leasing - e.g., Zipcar Licensing
Auctions - e.g. eBay
Data - e.g., Duedil
Transaction processing - e.g., Stripe
App downloads - e.g., Minecraft
In-app purchases - e.g., Clash of Clans, etc
We can work with every mobile apps` revenue model.
4xxi Clients & Portfolios
















4xxi Reviews
- All Services
- Web Development
- Mobile App Development
- Relevance
- Most Recent
- Rating: high to low
- Rating: low to high

Top development team
Review Summary
What is it about the company that you appreciate the most?
Excellent partnership and commitment to quality
Review for 4xxi
Review Summary
What was the project name that you have worked with 4xxi?
App Development Project

Amazing to work with. Super smart. Super responsive.
Review Summary
What is it about the company that you appreciate the most?
Speed. Quality of product. Responsiveness. Energy. Passion. Brains. Ability to quickly find quality candidates to fill various positions when we need to expand the development team.
What was it about the company that you didn't like which they should do better?
Nothing, honestly.

4xxi Exceeded Expectations
Review Summary
What is it about the company that you appreciate the most?
Easy to work with, extremely reliable and delivers.
What was it about the company that you didn't like which they should do better?
They are Russian. THey speak English but may not catch typos!

Woolmark Prize
Review Summary
The project started in December 2015 and was completed in 1 month. The project was delivered on time!
What is it about the company that you appreciate the most?
We just provided 4xxi the concept of the project and the designs. We needed: a website (backend and frontend) + server infrastructure setup & support. Due to the limited time we had a lot of calls to finalize the scope.