Online laboratories have traditionally been split between virtual labs, with simulated components; and remote labs, with real components. The former tend to provide less realism but to be easily scalable and less expensive to maintain, while the latter are fully real but tend to require a higher maintenance effort and be more error-prone. This technical paper describes an architecture for hybrid labs merging the two approaches, in which virtual and real components interact with each other. The goal is to leverage the advantages of each type of lab. The architecture is fully web-based and multiplatform, which is in line with the industry and the remote laboratory community trends. Only recently has this become technically feasible for graphic-intensive laboratories due to previous limitations in browser-based graphical technologies. This architecture relies on the recent HTML5 and WebGL standards to overcome these limitations, and makes use of the Unity technology. To ensure that the proposed architecture is suitable, we set requirements based on the literature, we compare it with other approaches, and we examine its scope, strengths, and weaknesses. Additionally, we illustrate it with a concrete hybrid lab and we evaluate its benefits and potential through educational experiments.