# Open rate

> The share of delivered messages for which the sender recorded at least one tracking-pixel load.

- **Category:** Measurement
- **Updated:** July 2026
- **Canonical page:** [https://emailbump.com/glossary/open-rate](https://emailbump.com/glossary/open-rate)

## Definition

Open rate is usually calculated as unique tracked opens divided by delivered messages. An open is inferred when a tiny remote image loads; it is not a direct record that a person read the email.

Image blocking can miss real reading, while Apple Mail Privacy Protection and other proxy systems can preload images without a person opening at that moment. The metric remains directional when compared carefully within similar audiences and environments.

## Why it matters

Open trends can reveal large changes in sender recognition, subject performance, or estimated placement. They should not be used alone for automation, inactivity deletion, or campaign success.

## How it works

1. The sender adds a unique tracking image URL.
2. An email client or privacy proxy requests that image.
3. The platform records the event and deduplicates unique recipients.
4. The count is divided by delivered messages and interpreted with known tracking limitations.

## Example: Typical calculation

```text
Sent:            10,000
Bounced:            200
Delivered:         9,800
Unique opens:      3,136
Open rate:       3,136 ÷ 9,800 = 32.0%
```

## Common mistakes

- Calling a pixel load proof that a person read the message.
- Comparing unlike audiences or message types as if they were controlled tests.
- Removing subscribers based only on no recorded opens.
- Optimizing sender names or subjects for curiosity that harms conversion or complaints.

## Key takeaways

- Open rate measures image requests, not human attention directly.
- Use it as a directional top-of-funnel signal.
- Pair it with clicks, replies, conversion, complaints, and customer activity.

## Related definitions

- [Click-through rate](https://emailbump.com/glossary/click-through-rate.md) — The percentage of delivered messages that produced at least one tracked link click.
- [Email subject line](https://emailbump.com/glossary/subject-line.md) — The brief message label that tells a recipient what an email is about before opening.
- [Sender name](https://emailbump.com/glossary/sender-name.md) — The display name shown beside an email address to identify the person, brand, or team sending.
- [Inbox placement](https://emailbump.com/glossary/inbox-placement.md) — Where accepted email is placed, such as the primary inbox, another inbox tab, spam, or junk.

## Related guides

- [How to A/B test email service providers without fooling yourself](https://emailbump.com/blog/ab-test-email-service-providers.md) — A rigorous guide to ESP evaluation: experimental design, reputation confounders, delivery and latency metrics, webhook reliability, failover, cost, and migration.
- [A simple framework for writing better subject lines](https://emailbump.com/blog/write-better-subject-lines.md) — Replace guesswork with a repeatable process for subject lines that are clear, specific, and worth opening.
- [Should your email come from a person or your brand?](https://emailbump.com/blog/person-vs-brand-email-sender.md) — A practical decision framework for founder emails, newsletters, lifecycle messages, and support—without using a human name as a growth trick.

## Primary sources

- [Apple: Mail Privacy Protection](https://support.apple.com/guide/iphone/use-mail-privacy-protection-iphf084865c7/ios)