What is Open Rate?
Open rate is an email metric showing the percentage of delivered emails that recipients opened, typically measured via tracking pixels, though increasingly unreliable due to privacy protections.
Open rate measures what percentage of your delivered emails were opened by recipients. It's calculated as: (Unique Opens ÷ Emails Delivered) × 100.
For example, if you send 1,000 emails, 950 are delivered (50 bounced), and 285 are opened, your open rate is 285/950 = 30%.
Open tracking typically relies on embedded tracking pixels—tiny images that load when the email is opened. However, this method is increasingly unreliable: - Apple Mail Privacy Protection pre-loads images, inflating open rates - Some clients block images entirely, underreporting opens - Gmail and others proxy images, limiting data collection - Corporate security tools may pre-fetch or block tracking
As a result, open rates are best used as directional trends rather than precise metrics.
Why Open Rate Matters
Despite its limitations, open rate remains a widely-used engagement metric. It helps you understand which subject lines resonate, optimal send times, and overall list engagement. For transactional email, open rates indicate whether critical messages are being seen. Just remember: the absolute number matters less than trends over time.
How Ark Handles Open Rate
Ark tracks opens via pixels but clearly documents the limitations. We show open data in your dashboard and send it via webhooks, letting you build your own engagement analysis. We recommend correlating opens with more reliable signals like clicks and conversions for complete engagement pictures.
Frequently Asked Questions
What's a good open rate?
It varies by industry and email type. Transactional emails typically see 40-60% open rates. Marketing emails average 15-25%. More important than benchmarks: compare against your own historical rates and look for trends.
Why did my open rates suddenly increase?
Apple Mail Privacy Protection (introduced in iOS 15) pre-loads tracking pixels, registering opens even when users don't read the email. If you saw open rates jump in late 2021, that's likely the cause.
Should I still track open rates?
Yes, but with caveats. Open rates still show relative trends and are useful for A/B testing subject lines (comparing relative opens, not absolute numbers). Just don't treat them as precise measurements or base critical decisions on small differences.
What's better: unique opens or total opens?
Unique opens (counting each recipient once regardless of how many times they open) is more useful for measuring reach. Total opens can indicate high engagement but may be inflated by automatic image loading.
Related Terms
Tracking Pixel
A tracking pixel is a tiny, invisible image embedded in emails that records when recipients open the...
Click-Through Rate
Click-through rate (CTR) is an email metric measuring the percentage of recipients who clicked a lin...
Email Deliverability
Email deliverability is the ability to successfully deliver emails to recipients' inboxes rather tha...
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