What is Subject line?
A subject line is the short line of text shown in the inbox that tells the recipient what the email is about and gives them a reason to open it.
It works together with the from name and the preheader. The three are read as one unit in the inbox, so a subject line that repeats the preheader wastes space, and one that contradicts the email body breeds distrust.
Clarity usually beats cleverness. A line that states the offer, the product or the news is easy to judge in a second. Curiosity can work, but a promise that the email does not keep teaches people to ignore you.
Length matters less than whether the key words appear early, since many apps cut off the end. Test one change at a time, and judge by clicks and revenue as well as opens, because opens are distorted by privacy features.
A worked example.
A hypothetical stationery shop is launching a notebook in a new colour. It tests 'The new sage green notebook is here' against 'Something green just arrived'. The first is plain and the second is vague. The team keeps the clearer line for the launch and saves the playful style for a low-stakes newsletter.
Common mistakes.
- Writing a misleading line that the email does not deliver on
- Judging the winner of a test on open rate alone
- Using all capitals or heavy punctuation that reads like spam
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