<p>Die swell is a well-known phenomenon occurring when a polymer melt is subjected to a constriction flow, resulting in an expansion of the melt as it exits an extrusion die. This flow-induced effect is ubiquitous in the field of extrusion-based polymer processing, including material extrusion-based additive manufacturing such as fused filament fabrication (FFF). However, its implications in FFF remain poorly understood, notably because the melt strand deposition flow occurs quite close to the printing nozzle exit, where the die swell does not happen freely (as for a simple extrusion flow) but in a confined layered flow. To better describe the relevance of this phenomenon in the context of FFF processes, we propose an examination of die swell in both free extrusion and confined flow conditions, where we underline the influences of the polymer molecular weight and processing conditions in the case of isotactic polypropylenes. A combination of rheological measurements, numerical flow analysis, and optical characterizations highlights significant swelling ratios at the exit of the printing nozzle in a typical range of FFF printing conditions. These results are counterbalanced by how little effects such die swells have on the final dimensions of the printed strands (the opposite is often hypothesized in the literature), as evidenced by cross-sectional analysis and transient lengths measurements. This study points to a different influence of die swell in confined FFF flow conditions, more related to the impact on interlayer adhesion and polymer chain orientation rather than the expected change in print dimensions.</p>