This study aims to explore the interrelation between the structural, molecular, and particulate attributes of alginic acid and its functional traits in direct compression, encompassing tabletability, compressibility, elasticity, deformation mechanism, and disintegration ability. Thorough characterization of two distinct batches of alginic acid was conducted, employing various techniques such as X-ray powder diffraction, Fourier-transform infrared spectroscopy, thermogravimetric analysis, scanning electron microscopy, 1H nuclear magnetic resonance, size exclusion chromatography – multi-angle light scattering, viscosimetry, carboxylic acid titration, powder flowability, true density, and laser granulometry. The findings indicated that molecular weight appears to influence tablet properties, with the lowest molecular weight alginic acid yielding the hardest tablets and exhibiting the lowest elastic recovery. These results underscore the potential utility of alginic acid as a filler excipient in tablet formulations. Additionally, the disintegration properties of the tested materials were found to be comparable to those of commercial superdisintegrants (Glycolys® and Kollidon Cl®), although not correlated with their swelling force. In conclusion, it is highlighted, for the first time, that determining alginic acid's molecular weight is crucial for applications in direct compression, particularly in achieving tablets with consistent strength.