Top 15 Third-Party API Integration Companies in Europe (2026)

Gilzor works on custom software projects where third-party API integrations are usually part of a wider product rather than an isolated task. Its work covers web and mobile applications, internal tools, and platforms that connect to payment systems, analytics services, CRM software, communication tools, maps, booking systems, and other external platforms. The company also considers data flows, integration logic, performance, error handling, testing, and post-launch maintenance as part of the integration process.

The approach is suited to startups, SMBs, and product teams that need external services incorporated into a custom application. Gilzor combines integration work with business analysis, architecture, development, QA, and ongoing support, which can be useful when API work is closely tied to the product's overall architecture.

ScienceSoft provides custom API development and system integration services for applications that need to exchange data with third-party systems. Its integration work covers API development, cloud integration, application integration, middleware, and enterprise software environments. The company also documents experience with real integration projects, including a reusable REST API service created for integration with Visma Global ERP.

Its European presence includes offices in Riga, Vantaa, and Warsaw. That makes ScienceSoft relevant for European organizations looking for a larger engineering provider with experience in enterprise integration, custom APIs, and complex software environments.

OSKI Solutions focuses heavily on software integration, with services covering APIs, databases, SaaS products, legacy platforms, middleware, webhooks, data synchronization, and ETL. Its API offering includes REST and GraphQL integrations, third-party services, API authentication, versioning, documentation, and resilience patterns such as retries and change tracking.

Its integration work includes a portal that connects more than 10 external APIs and a daily profile synchronization process handling 15,000 records. OSKI is an Estonian-Ukrainian company serving European and US businesses, with Tallinn as its European location.

Future Processing works on software and systems integration as part of broader technology delivery. For Interparking, the company implemented an API-based loyalty solution while moving an older system toward cloud-based microservices. The project also involved ongoing system maintenance and data migration.

The company is headquartered in Gliwice, Poland, and has further European locations including Germany, the UK, and Sweden. This geographic setup can suit organizations that want a European delivery partner with experience working across distributed teams and integration-heavy modernization projects.

Itexus has a strong focus on fintech and financial software, with API integration services centered on banking, payments, trading, and financial data. Its work includes integrations for neobanks, payment providers, robo-advisors, and trading systems, using platforms such as Plaid, Yodlee, Stripe, Adyen, and Bloomberg.

Its integration work includes payment gateways, open banking, transaction synchronization, webhook handling, tokenization, reconciliation, and other financial workflows. With a Warsaw office and a portfolio built around fintech projects, Itexus is a natural fit for API integrations where financial data and transaction processing are central requirements.

Netguru provides custom API development and integration services for applications that need to communicate with external systems. Its service offering includes SaaS, eCommerce, CRM, ERP, healthcare, mobile, and cloud API integrations, with experience across REST, GraphQL, SOAP, and other API standards.

The company also has relevant integration work in production. For example, Netguru built a middleware layer connecting a major automobile club's web and mobile applications with Solaris for card registration, verification, and transactions. Its headquarters are in Poznań, Poland.

A-Listware handles application integration as part of its broader software engineering services. Its current offering includes application integration, custom software development, legacy modernization, and other engineering services, while its European-focused materials specifically mention connecting enterprise applications, third-party software, and legacy systems.

The company operates a UK office in St. Leonards-On-Sea and works on integrations involving APIs, enterprise applications, real-time data, workflow automation, and legacy systems. It can therefore fit projects where a third-party API connection is one component of a wider software or application integration requirement.

Inoxoft offers dedicated IT and software integration services covering API integration, third-party software integration, cloud integration, data migration, enterprise application integration, and microservices integration. Its API work focuses on connecting applications and systems through secure APIs, while the third-party integration offering covers tools such as CRM and ERP systems.

The company has European offices in Poland, Estonia, and Ukraine. Its integration services are relevant for projects where external APIs need to coexist with existing enterprise applications, cloud infrastructure, or microservice-based software.

Mobian is a European software development company focused on mobile and AI products, with API development and third-party integrations included in its development services. Its services include custom mobile and web applications, API development, and third-party integrations that connect applications with external systems.

The company has a Tallinn, Estonia address and works across areas such as healthcare, fintech, logistics, and enterprise software. This makes Mobian more relevant to integration projects where the API layer is closely tied to a mobile or web application rather than a standalone enterprise integration platform.

ELEKS provides system integration services covering enterprise application integration, cloud integration, business process integration, middleware development, legacy integration, and system-to-system connectivity. Its service materials specifically identify APIs as a way to connect businesses with third-party services while maintaining security and performance.

The company has a substantial European presence, including offices and development centers in Estonia, Poland, Ukraine, Croatia, and other locations. That makes ELEKS a suitable option for more complex integration programs where third-party APIs form part of a wider enterprise architecture.

Geniusee provides software integration services that include system integration, API integration, cloud integration, and legacy integration. Its API offering connects third-party services, CRM systems, and internal tools, while the broader integration practice also covers data synchronization and cloud environments.

The company has European offices in Warsaw and Stockholm and works with startups and enterprises across several technology areas. Its integration services can be a fit for organizations that need API connectivity as part of a larger custom software or cloud project.

Intellias provides API integration services that connect applications with third-party systems, cloud platforms, and internal software. Its API modernization work covers implementation, integration, security, performance, governance, and ongoing management, while its platform engineering offering also includes API and system integration.

The company has offices across Europe, including Poland, Germany, Portugal, Spain, Bulgaria, Croatia, and the UK. Its services include integrations for banking, telecom, travel, and other large-scale digital platforms, making the company relevant to organizations with complex API ecosystems.

net-devs provides enterprise software engineering across .NET, JVM, Node, Python, and Go, with a focus on system and API integration. Its work includes an integration layer for the BGU student portal that connects more than 10 external APIs for schedules, grades, payments, assignments, and Moodle SSO.

Its work with Disctopia also involved unifying separate backend logic behind one API and consolidating authentication through Auth0. Based in Warsaw, net-devs is particularly relevant for teams that need third-party integrations embedded into a larger enterprise application rather than handled as a standalone connector. 

SoftPro provides custom software and web development services from Warsaw, with its integration offering covering communication between external business systems and websites or applications. Its API-related services include integrations with CRM, ERP, databases, analytics systems, and other business software.

The company's services include custom software, web application development, cloud development, and ongoing maintenance. This combination is relevant for businesses that need third-party connectivity built into a broader website or application project.

Lengreo combines technology and digital marketing services, with API development and integration included in its mobile application development offering. It builds custom APIs and integrates applications with third-party services, CRM systems, ERP platforms, and payment systems.

The company has locations in Amsterdam and Kyiv and offers in-person meetings in Central Europe. Lengreo is suited to projects where third-party API work is part of a mobile application, SaaS product, website, or broader digital development engagement.