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Email Open Rate

Email open rate is the percentage of delivered emails that recipients open, driven primarily by the subject line, sender name, and preview text. While modern privacy features make open rates less precise than they once were, they remain a useful directional signal for subject-line performance.

Why it matters for developers

No one reads an email they do not open, so open rate gates the entire value of your list. It is also the cleanest place to test copywriting, since the subject line is a tiny, high-leverage experiment.