Using video recordings of a collaborative writing task carried out on a shared computer in an English as a foreign language class, this chapter explores the "epistemic ecology" of correcting spellings, where knowledge of spelling is unevenly distributed, i.e. the knowledge available to the typist, the other student (the non-typist) and the spell-checker. Three possible assumptions are addressed: (1) that the inbuilt spell-checker offers help in spelling; (2) that two "writers" both contribute to ensuring that spellings are correct; (3) that the potentially uneven distribution of knowledge about spelling between the current typist, the non-typist and the spell-checker does provide for "epistemic progression" (i.e. knowledge gains) and thus learning opportunities when genuine spelling problems arise. The findings mainly corroborate these assumptions, but they also uncover a number of issues that affect and sometimes confound the potential for correction and learning. For example, a common problem in an otherwise non-English medium setting is that the language tools are wrongly configured (or they are not switched on). Moreover, the timing of the correction process typically gives the typist the first "opportunity space" to correct, followed by the spell-checker and lastly the non-typist. There is also evidence from this study that not all students are familiar with how the language tools (including the spell-checker) work and what help can be had. This suggests the need to teach the basic functions and initiate awareness-raising activities about the potential gains, issues and pitfalls of both the spell-checker and collaboration. [For the complete volume, "Classroom-Based Conversation Analytic Research: Theoretical and Applied Perspectives on Pedagogy. Educational Linguistics. Volume 46," see ED660574.]