APIs often sit behind the parts of a product users never see, but they have a big effect on how reliably systems exchange data, connect with third-party services, and scale. This list covers API development companies in Europe working on everything from REST and GraphQL interfaces to integrations, backend architecture, authentication, testing, and legacy API modernization.
Gilzor treats API development as part of the wider product architecture rather than an isolated backend task. Their work includes designing interfaces that connect web applications, mobile products, internal systems, and third-party services. They define endpoints, data models, authentication, access rules, and how information moves between different parts of a product.
For new products, they can plan the API structure alongside the rest of the system from the beginning. With existing software, their work may involve adding integrations, extending endpoints, improving performance, or cleaning up API logic that has become difficult to maintain as the product has grown.
SCAND has a dedicated API development practice covering REST, GraphQL, gRPC, and web APIs. Its services extend beyond creating endpoints from scratch, with API integration, modernization, testing, documentation, and ongoing support included in the company's current offering.
The company works with APIs used in SaaS, fintech, healthcare, logistics, ecommerce, and enterprise systems. It also handles integrations involving CRMs, ERPs, payment gateways, cloud platforms, analytics services, and other business software. This gives SCAND a fairly broad fit for projects where API development is closely tied to a larger custom software environment.
OSKI Solutions has a dedicated API development service covering REST and GraphQL interfaces, webhooks, gRPC, authentication, versioning, documentation, rate limiting, and backend business logic. Its work ranges from designing greenfield APIs to consolidating integrations and shared backend services.
The company's published projects provide useful examples of this approach. One project unified two separate products behind a shared API and Auth0 identity layer, while other work includes high-volume data synchronization and headless backend architectures. Its stack for API projects includes .NET, Node.js, NestJS, GraphQL, OpenAPI, Auth0, SQL Server, PostgreSQL, and Docker.
Softjourn covers the full API lifecycle, from design and architecture through implementation, integration, monitoring, documentation, and support. The company works with RESTful APIs, GraphQL, and gRPC, and also takes on modernization projects where existing interfaces need to be updated or reorganized.
Its API work is closely connected with fintech, ticketing, and media and entertainment software. Available services include mobile and cloud APIs, third-party integrations, API testing, traffic management, security, documentation, and performance monitoring. Softjourn also maintains development operations in Europe, including Ukraine and Poland.
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Ficode focuses on custom API development and integrations for systems where performance and communication between multiple services matter. Its current offering covers REST APIs alongside SOAP-based integrations, authentication methods such as OAuth 2.0 and JWT, API gateways, documentation, testing, and post-development maintenance.
The company's architecture work also extends into microservices, messaging queues, load balancers, Docker, and Kubernetes. That makes its API services relevant to businesses working with distributed systems rather than only straightforward point-to-point integrations. Ficode operates from the UK and provides API services internationally.
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net-devs works primarily on enterprise software, with backend engineering spanning .NET, JVM, Node, Python, and Go. API development sits within that broader engineering work, particularly where businesses need shared services, integrations, or new interfaces around existing systems.
Published project work includes consolidating duplicated backend logic into a single REST API consumed by two separate products. The company also handles third-party API integrations and high-volume workflows, including systems where queue management, retries, and external API rate limits need to be considered. net-devs is based in Warsaw, Poland.
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SoftPro is a Warsaw software development company working mainly with Microsoft technologies such as Azure, ASP.NET, .NET Core, and C#. Its services cover custom software, web applications, backend development, cloud solutions, and system integration.
API work tends to appear within those larger software projects rather than as an isolated service category. The company has experience with enterprise platforms, CMS implementations, backend development, cloud migration, and integrations between business systems. This makes it more relevant to teams that need APIs as one part of a broader .NET or Microsoft-based application project.
Innowise provides a dedicated custom API development service covering consulting, custom backend interfaces, mobile APIs, web APIs, and a broad range of integration work. Its integration capabilities include SaaS, IoT, CRM, ERP, payment, cloud, and LLM APIs.
The technical scope is equally broad. Innowise works with REST, GraphQL, SOAP, and gRPC, along with OAuth2, JWT, API gateways, databases, cloud platforms, and CI/CD tooling. It also offers API testing, documentation, deployment, monitoring, and support, making it suitable for companies that want one provider to handle several stages of the API lifecycle.
SoftTeco develops APIs for web, mobile, cloud, and custom software projects. Its API work covers interface design, third-party integrations, testing, automation, and maintenance, with support for REST, SOAP, and GraphQL architectures.
The company is useful to consider when API development is part of a broader application build rather than a standalone interface project. Its published service coverage includes public, private, and partner APIs, allowing teams to use APIs internally, expose selected functionality to partners, or connect products with external platforms.
DSP approaches API work mainly through enterprise integration, cloud, databases, and data management. Rather than focusing primarily on consumer-facing APIs, its work is relevant where interfaces need to connect enterprise applications, databases, cloud services, and existing business infrastructure.
This is a more infrastructure-oriented option than some of the API specialists on the list. DSP works across Oracle, Microsoft, and cloud environments, with APIs used to support controlled data exchange between systems. The company is based in London.
Itexus brings a narrower industry focus to API development, concentrating heavily on financial software. Its API integration services cover open banking, payments, trading, market data, KYC and AML services, and other connections commonly required by banks and fintech products.
The company works with platforms and APIs such as Plaid, Stripe, Adyen, Bloomberg, PayPal, Braintree, and banking-as-a-service providers. Backend work includes Java, .NET, and TypeScript, with API contracts and integration requirements defined as part of the delivery process. Itexus has development operations in Europe and serves financial organizations across European markets.
Leobit's API experience can be seen across its custom software portfolio. The company has developed external API services, RESTful interfaces for web and mobile applications, and integrations with platforms including Stripe, SendGrid, DocuSign, HeyGen, Google Maps, and industry-specific services.
Its projects also show API work inside modern .NET and Azure architectures. One example involved developing an external API that allowed third-party companies to connect with an insurance platform, while another used RESTful endpoints and Azure Functions in an AI video translation workflow. Leobit has a development center in Lviv, Ukraine.
Data Menu is a UK company with a particularly API-focused service offering. It designs and builds REST and GraphQL APIs, internal interfaces, public APIs, data APIs, and commercial API products. The company also works on the surrounding infrastructure, including authentication, rate limits, logging, monitoring, versioning, documentation, and hosting.
There is a noticeable data angle to its work. Alongside conventional integrations, Data Menu develops APIs for ecommerce information, business data, live data, validation services, automation, and other structured datasets. It can also help businesses turn internal data or workflows into APIs intended for external customers.
GoodCore provides custom API development and integration as part of its wider software engineering work. Its process starts by defining what data or functionality needs to be exposed, followed by development, controlled testing, documentation, and integration support.
The company can also connect applications with existing third-party APIs and services. Its published API offering places particular attention on endpoint testing, error handling, security, documentation, and the developer experience around consuming an API. GoodCore's UK head office is in Croydon.
Appoly offers API development as a defined service, with work covering custom interfaces and connections between existing software platforms. The company develops RESTful and SOAP APIs and also handles third-party integrations when businesses need existing applications to exchange information automatically.
Documentation and ongoing maintenance are included in its API offering. This can be useful for businesses that need more than the initial build and expect integrations to change as external platforms, internal systems, or operational requirements evolve.
A-listware combines API-related engineering with broader custom software development and team augmentation. Its web development offering includes backend development using PHP, .NET, Java, Python, Node.js, and Go, as well as API integration for connecting web applications with corporate and third-party systems. The company also works on application integration, modernization, cloud development, QA, and infrastructure services.
For API-heavy projects, A-listware can be a practical option when the interface is part of a larger backend or application development effort rather than a standalone deliverable. Its published European software development material specifically references backend engineering, API design, integration strategies, cloud infrastructure, automated testing, and ongoing operations.
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Mobian Studio is a European software development partner working across mobile products, AI systems, enterprise backends, APIs, cloud infrastructure, and QA. API engineering forms part of its end-to-end product development model, allowing the same team to handle the backend interfaces alongside mobile applications and other components of the product.
Its work is particularly relevant where APIs need to connect new software with existing infrastructure. Mobian explicitly includes legacy integration in its delivery model and lists experience with areas such as HL7/FHIR integrations, payment flows, and enterprise systems. The company works with IT, healthcare, fintech, and logistics projects and offers both outsourced delivery and engineers who join an existing development team.
The right API development company depends less on the length of its service list and more on how well its experience matches the system being built. A fintech platform may need strong knowledge of payment, banking, and authentication APIs, while an enterprise project could put more weight on legacy integration, cloud infrastructure, data exchange, and long-term maintainability.
The companies covered here approach API development from different angles. Some focus on API-first products and backend architecture, while others handle APIs as part of larger web, mobile, SaaS, or enterprise software projects. Before choosing a team, it is worth looking closely at its experience with the API technologies you plan to use, similar integration challenges, security requirements, documentation, testing, and post-launch support. A well-designed API should not simply connect two systems today. It should remain understandable, maintainable, and practical to extend as the product grows.
