How to write subject lines that get opened
You can write the best email of your life and it won't matter if nobody opens it. The subject line — plus the preview text beside it — does the heavy lifting in the inbox. This guide covers what actually moves open rates, and what quietly hurts them.
Keep it short and front-load the value
Most inboxes, especially on mobile, truncate subject lines somewhere around 40–60 characters. Anything important that lands after the cut-off might as well not exist. Put the hook first.
Short doesn't mean vague. 'Your order shipped' beats 'An update regarding your recent purchase with us' on every axis: clarity, length and honesty.
Lead with curiosity or a clear benefit
Two things reliably earn an open: a concrete benefit ('Save 3 hours on your next report') or genuine curiosity ('The mistake costing you 20% of opens'). Pick one lane per subject line — trying to do both usually muddies the message.
- Benefit-led: promise something useful and specific
- Curiosity-led: open a loop the email then closes
- Avoid vague hype ('You won't believe this!') — it reads as spam
Use the preview text as a second subject line
The preview (preheader) text sits right next to the subject in most clients and is prime real estate that too many senders waste on 'View in browser'. Treat it as an extension of the subject that adds detail or a second hook.
Personalize with substance, not just a first name
Dropping '{FirstName}' into a subject line is table stakes and increasingly ignored. Real personalization uses what you know: the product they browsed, the city they're in, the plan they're on. Relevance is the personalization that actually lifts opens.
Steer clear of spam triggers and ALL CAPS
Excess punctuation, ALL-CAPS words, and classic trigger phrases ('FREE!!!', 'ACT NOW', '$$$') raise your spam-filter risk and cheapen the message. Emoji can help or hurt depending on your audience — test, don't assume.
Frequently asked questions
What's a good open rate to aim for?
It varies widely by industry and list quality, but a healthy, engaged list often sees open rates well above the 20% range. Focus on your own trend over time rather than a universal benchmark — and remember open tracking has become less precise since privacy features like Mail Privacy Protection.
Do emojis in subject lines help?
Sometimes. They can boost visibility for some audiences and annoy others. Test them against your own list rather than following a blanket rule.
Should I A/B test subject lines?
Yes — it's the cleanest way to learn what your specific audience responds to. Change one variable at a time so the result is unambiguous.
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