Interactive exercises for the English grammar topics learners search for and get wrong most often — ranked by real search demand, learner-error-corpus data, and teaching attention. Free, no sign-up, for learners anywhere.
When to use a/an, the or no article — the single most common ESL error across all levels (A1–C1). Reading, gap-fill and free writing.
More exercises coming soon. The full topic list — ranked by evidence, Tier 1 first — lives in esl-grammar-pool.json. Remaining Tier 1 ("Big Eight"):