Quantum computers could provide breakthroughs in many disciplines. However, the number of qubits needed for a useful quantum computer, one that could compete with a classical PC in solving complex computational problems, is in the hundreds of thousands. Silicon spin qubits are an appealing alternative to competing qubit technologies. The EU-funded QLSI project aims to demonstrate that silicon spin qubits are a compelling platform for scaling to very large numbers of qubits. Demonstration activities will focus on the following: 16-qubit quantum processors based on modern semiconductor manufacturing techniques; high-fidelity single- and two-qubit gates; quantum computer prototypes with online open-access for the community (up to 8 qubits available online); documentation of the detailed requirements to address scalability towards large systems > 1 000 qubits.