This thesis aims to analyze how interfacing affects viewer experiences and viewer positions, and how glitch art online makes that effect visible. Glitch art is concerned with disruptions in the systems that govern how for instance photography is produced, circulated and displayed in a digital image flow. The system’s usually undisrupted operation emerges through the friction created between the key components of the study: the viewer, the photo-based mediation, and the inter­face where the two meet. These components are encircled by the relation between individual and system, whose increased integration with one another requires a sharper eye: a tactical spectatorship in response to how the interface of the image flow can turn the individual into a part of the system. The unfolding of such a spectatorship is in­vestigated through three questions: What can a viewer see and do by interfacing with the web­site, and with what means? How is the photo-based material on the web­site produced, dis­played and concept­ualized? How does the website and its photo-based material – glitched and not glitched – position the viewer haptically and epistemologically? With a cross disciplinary approach, three media phenomenological case studies present glitch artworks­ in an online environment. The case study on Phillip Stearns’s project Year of the Glitch concerns the web­site’s index and archive pages as well as still images with a focus on camera reconstruction, verbal con­cept­ualization, and image materiality. The case study on Rosa Menkman’s website Sunshine in My Throat includes index and artwork pages, two art­works with still and moving images as well as a thema­ti­za­tion of the entire online environ­ment being glitched. The case study on Evan Meaney’s project Ceibas Cycle focuses on the index page and an interface-based artwork, two video works as well as a portfolio of photo­graphs that are not glitched. The timeliness of the case study materials – created between 2004 and 2012 – is anchored in systems aesthetics, in which technical problems are explored as a cultural critique since the 1960s. The quali­tative analysis both emphasizes and problem­atizes experience, as a complement to quantitative studies about images in relation to a digital flow. The study analyzes how glitch art shapes experiences both by follow­ing the interface and by disrupting it. The effect of the underlying system thus appears in a material that has not yet been given an in-depth art historical analysis with a particular focus on the individual viewer. With such a focus, glitch is conceptualized as systemic friction in this study, which clarifies how the artworks online produce knowledge about the interface by providing the individual with a possibility of creating tactical breaks into the image flow. The results of the study consist of the ways of seeing that develop such a possibility – and they gain relevance as they make visible how the flow usually operates in invisible ways. These results point out that the experience of the artworks – and by ex­ten­sion, other experiences of images online – can alert viewers to their own activity within the image flow. If the system sets boundaries for experiences of and through the interface, a tactical spectatorship becomes possible when a glitch gives the individual an opportunity to try different positions towards these boundaries.