The aim of this text is to analyse various aspects of an error, understood as a collapse of form and content both in the 20th century and contemporary art, the latter influenced by post-digital (un)awareness. Art history teaches us that the avoidance of formal errors, crucial in the process of academic art education became irrelevant with the arrival of the first avant-gardes. This opened the way for artists to deal freely with the medium, or even act against the medium, not avoiding an error but rather embracing its surprising consequences. Therefore, a dilettante attitude disseminated rapidly across culture, allowing artists to make inspiring mistakes and find unexpected beauty in roughness and freedom in disorder. From the perspective of computing history, an error has always been a problem for coders and an annoyance for software users. The idea of making the most of technical limitations was discovered by net.art pioneers; later those mistakes were so appealing that a new genre was formed: glitch art. Nowadays artists produce so-called glitch art in their online and offline practice, using distortions resulting from errors in programming or the digital origin of images. Error-based artworks can be judged on criteria other than traditional, helping us find aesthetic joy in the collapse of forms. An intentional language mistake, just like the one made by Dada poets, reminds us that an imperfect message may reveal the hidden, conceptual framework of an apparently seamless structure. Post-digital error is, on the other hand, a paradox; being the creation from scratch of a seemingly erroneous object whose idea comes from digital vocabulary that is treated as a starting point to the planned collapse.