Free AI email subject line generator
Updated
Describe the email, pick a tone, and get eight options. Character counts are shown so you can see what fits.
AI can get things wrong, so read and edit before you send. Do not enter passwords, personal data or confidential details. What you type is sent to Inboxili and to an AI provider to write the result, and is not stored by Inboxili. Free use is limited per visitor.
What makes a subject line work
- Say what is inside. A subject that does not match the email trains people to ignore you.
- Front-load the key words. Phones cut the end off.
- Avoid spam patterns. All capitals, repeated punctuation and words such as "FREE!!!" attract filters and look cheap.
- Use specifics. "Your invoice for October" beats "Important update".
- Match the email type. Transactional subjects should be plain and searchable, such as "Your Acme verification code". Marketing subjects can carry more personality.
Test, do not guess
Send two subjects to two halves of a segment and compare click rates rather than opens, since open tracking is imperfect. The analytics page explains which numbers are reliable.
The AI assistant in the Inboxili campaign editor also suggests preview text and call-to-action labels alongside subject lines. See the AI email assistant.
Frequently asked questions
- How long should a subject line be?
- Short enough to show in full on a phone, which is roughly 40 to 60 characters. Put the important words first.
- Will these subject lines improve my open rate?
- There is no guarantee. A good subject line is clear about what is inside. Test options against each other on your own audience.
Write and send emails in Inboxili
Create a workspace, verify a domain, and make your first API call.