Writing a preheader
Your subject line gets most of the attention, but the preheader is the short preview text that appears right next to it in the inbox. Most email clients display it as a grey snippet after the subject line, before a contact opens the email.
If you leave the preheader empty, the email client pulls in the first readable text from your message. This is usually something unhelpful like "View this email in your browser", a navigation link, or an image alt tag. Setting a deliberate preheader takes about 30 seconds and meaningfully increases the chances of your email being opened.
What the preheader is for
Think of the preheader as a second subject line. The subject line captures attention; the preheader gives the reader a reason to act on that attention. Together they form the first impression your email makes.
A good preheader does one of three things:
- It adds context the subject line left out.
- It states the value or offer directly.
- It includes a short call to action.
What it should not do is repeat the subject line word for word. If your subject line says "Your order has shipped", a preheader that says "Your order has shipped" wastes the space entirely. Instead, add something new: "Estimated delivery: Thursday. Track your package here."
How long should a preheader be?
Keep your preheader between 40 and 130 characters. Most email clients display around 40 to 90 characters in the inbox view before cutting off, depending on screen size and device. The Flexmail preheader field accepts up to 150 characters.
Put the most important information first. A preheader that opens with a discount or a deadline lands well even when truncated. One that buries the key point at the end often does not.
How to set a preheader in Flexmail
You set the preheader in the first step of the campaign wizard, right below the subject line field.
- Open your campaign wizard and go to step 1.
- Find the Preheader field below the subject line.
- Type your preheader text. The field accepts up to 150 characters.
- Continue to the next step as usual.
Support tip You can use personalisation placeholders in your preheader in the same way you would in a subject line. Add #firstname# to include each contact's first name. See "Personalising your subject line" for the full list of available placeholders.
Examples
Here are a few examples of how subject line and preheader can work together:
| Subject line | Preheader |
|---|---|
| Your order has shipped | Estimated delivery: Thursday. Track it here. |
| New collection: summer essentials | Free shipping on all orders this week. |
| Your monthly report is ready | Open rates up 12% compared to last month. |
| Webinar this Thursday: grow your list | Register now. 47 spots left. |
| Sophie, your exclusive offer is inside | 20% off, valid until Sunday midnight. |
Common mistakes to avoid
- Leaving the preheader empty. The email client will pull the first readable text from your message, which is rarely what you would choose.
- Repeating the subject line. This wastes the space. Give the contact a new reason to open.
- Writing a preheader that is too short. A preheader under 30 characters will be padded with random text from your email by most clients. Aim for at least 40 characters.
- Putting unsubscribe or legal text at the very top of your email body. Some senders do this, and it then appears as the preheader. Move that text lower in the email.
Next steps
- See "What makes a good subject line?" for guidance on writing subject lines that work well alongside your preheader.
- See "Using the AI subject line and preheader generator" to get Flexmail to suggest subject line and preheader combinations based on your email content.
- Set up an AB test on your next campaign to compare two subject line and preheader combinations and measure which gets more opens.