Open Rate
Whether your subject line and send time earned the first three seconds.
What it means
Open Rate is the share of your delivered emails that someone opened at least once. It's measured against DeliveredDeliveredHigher usually means a larger reachable audience., not against everyone you tried to reach, so bounces never drag it down. Each recipient counts once however many times they reopen the message.
Show the math
Formula and a worked example
Open Rate = unique opens ÷ DeliveredDeliveredHigher usually means a larger reachable audience..
Unique opens counts each recipient once, however many times they reopen the message.
Worked example. A campaign goes to 10,000 profiles. 400 bounce, so 9,600 are delivered. 3,360 people open it. Open Rate = 3,360 ÷ 9,600 = 35%. That send earned €4,800, which works out at €1.43 per opener.
An open is registered when the tracking image loads. Apple Mail pre-loads that image whether or not anyone reads the message, so part of this number is machinery rather than attention.
It answers the question
Did anyone notice this send? A low rate means most of the list never read it, so nothing downstream had a chance.
Why it matters
It's the shop window. Nobody buys what they didn't stop to look at, and every click and order in the row below starts with someone deciding this message was worth opening.
It's also your earliest deliverability alarm. Inbox providers score you on engagement, so a steady slide across similar sends can mean messages are drifting towards the spam folder — weeks before revenue shows it.
What good looks like
No universal standard applies, and the number moved for everybody the day Apple started pre-loading images. Judge it against your own last ten sends of the same type, to the same kind of segment — a win-back to recent buyers and a full-list campaign are not comparable. The direction over a quarter tells you far more than the level in any single week.
How to improve it
| Lever | What you do | Expect | How long | Watch out for |
|---|---|---|---|---|
| Fast Test two subject lines per send | Split the send, keep the winner, write the next pair from what won | 3–6 points on the winning variant | 2 weeks | Curiosity and discount lines win these tests. They pull in openers who never intended to buy, so Click Rate per opener usually falls. |
| Fast Send campaigns to the 90-day engaged only | Exclude anyone who hasn't opened or clicked in three months | Rate up sharply from the next send | 1 send | Reach shrinks with it. Delivered drops, and total campaign revenue can fall even while the rate looks better. |
| Slow Sunset the names that never engage | One last-chance send, then suppress anyone silent for 6–12 months | Rate up and inbox placement improves across everything | 4–6 weeks | You permanently give up names you paid to acquire, and list size is usually the first number anyone outside the team asks about. |
| Slow Authenticate and warm a sending domain | Dedicated sending subdomain with DKIM, SPF and DMARC, then ramp volume slowly | More messages reach the inbox instead of spam, lifting every send | 1 quarter | The warm-up caps how much you can send for weeks, so reach and revenue dip before they recover. |
Every lever costs something somewhere. The last column is the one to read twice.
Read it with
Open Rate alone says people looked. Beside clicks, it says whether the subject line told the truth.
The envelope and the letter agree
People opened and then acted. The promise on the outside matched what was inside, which is the only combination worth repeating.
Opened, then ignored
The subject line over-sold. You bought attention you couldn't pay off, and shoppers remember that the next time your name appears.
Small crowd, right crowd
Fewer people looked, but the ones who did wanted it. Often a sign the offer is sharp and the subject line is burying it.
Nobody's home
Both falling together across several sends is rarely a writing problem. Look at authentication, list quality and how often you're sending.
Together they tell you whether attention was earned or extracted. Opens up while unsubscribes also climb means the subject line pulled people in and the message disappointed them — you spent list to buy a look. Opens up with unsubscribes flat is the same headline for free.
A rate next to its own denominator. A climbing Open Rate on falling Delivered means you're mailing a smaller, keener slice — better numbers, less reach, and no evidence the writing improved. Read the pair before you credit a copy change.
Common misreads
Apple pre-loads tracking images for its users, which registers as an open nobody made. A shift in which devices your list uses moves this number with the copy untouched. Check clicks before you credit the subject line.
It depends entirely on who you sent to. A back-in-stock alert to 400 waiting shoppers should beat a full-list campaign comfortably. Compare like with like or the number tells you nothing.
It's a poor absolute number and a useful relative one. Your own trend across similar sends still flags a deliverability problem earlier than anything else on the Klaviyo page.
Also called
Unique open rate · opens ÷ delivered · email open rate
See yoursYour Open Rate for every campaign and flow in the period, beside the delivery count it's measured against.
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