The now ubiquitous use of advanced Web 2.0 tools in writing and the emergence of automated error flagging applications with affordances far beyond Word Processing requires some attention from both L2 researchers and L2 tutors, especially when both native (skilled) writers and non-native (less skilled) writers have, reportedly, started to use various commercial and freemium technological tools that claim to provide automated written corrective feedback. In fact, little is known about tracking writers’ editing behaviour when automated error flagging is in place and whether such behaviour would vary between native and non-native writers. Using a pre-post activity interview, an IELTS writing task 2 and screen capture software, the current case study compared the editing behaviours of native and non-native speakers of English when Grammarly was used. Major results revealed that native speakers had overall more flagged errors than non-native speakers did, but the latter group had more grammar errors flagged. However, the two groups followed a similar pattern in reacting to the flagged errors. Both native and non-native writers accepted suggestions from Grammarly. The study also suggests that evidence is needed with regard to teachers’ roles in and learners’ uptake from error flagging applications.