The European X-ray Free-Electron Laser (XFEL) is being built starting from the DESY Hamburg campus. The European XFEL will adopt the Self-Amplified Spontaneous Emission (SASE) process to generate extremely brilliant and ultrashort pulses of spatially coherent X-rays with tunable wavelengths down to 0.1 nm. The application will be a relevant step forward for scientific experiments in various disciplines. The facility components are distributed along an essentially linear geometry of 3.4 km length (with about 5.5 km of tunnels), starting on the DESY campus in the northwest part of the city of Hamburg and ending in the town of Schenefeld in the neighboring federal state of Schleswig-Holstein where the experimental hall is located. European XFEL shareholders contribute to construction costs in cash or in kind. In-kind contributions (IKCs) can take the form of component delivery, secondment of staff, or both. In 2014, 9 different countries are contributing 78 IKCs by 21 institutes for a total of 575 million euro (M€), while a few other proposals are in preparation.The beam vacuum system of the accelerator contains sections operated at room temperature as well as at 2 K in the areas of the superconducting accelerating structures. Moreover, some of the experimental instruments have specific UHV requirements.An overview of the IKC project will be provided with a special highlight on the vacuum technology contributions.