Email subject line tester
Paste a subject line and preview text to see exactly how they’ll be truncated in the inbox — plus a check for the wording that trips spam filters.
Your email
Inbox previews
Gmail desktop
Oitomail
Your weekly product digest is ready — See what changed and what to do next — 2 minute read.
Mobile (iOS Mail)
Oitomail
Your weekly product digest is ready
See what changed and what to do next — 2 minute read.
Checks
No issues found — this subject line looks inbox-ready.
Subject: Your weekly product digest is ready
Preview: See what changed and what to do next — 2 minute read.Send email that actually converts
Oitomail lets you A/B subject lines per segment, preview them against a real contact record, and stop a sequence the moment the goal is hit.
Start 7-day trialWhat makes a subject line work
- Front-load the value in the first 30 characters — that’s all a phone shows.
- Treat preview text as a second line of copy, never a repeat of the subject.
- Personalise with a real attribute (first name, plan, last action), not a generic token.
- Avoid all-caps, stacked punctuation and cash-flavoured wording.
Frequently asked questions
How long should an email subject line be?
Aim for 30–50 characters. Most desktop clients cut off around 60 characters and mobile inboxes often show only 30–40, so front-load the meaningful words.
How long should preview text be?
Between 40 and 100 characters. Preview text is shown next to or under the subject line and should extend the subject rather than repeat it.
Do emojis hurt deliverability?
One well-placed emoji is fine and can lift open rates, but stacking several — especially with all-caps or excessive punctuation — is a common spam-filter signal.
Does this tool store my subject lines?
No. Everything is calculated in your browser; nothing is sent to a server.
Turn activity into retained revenue.
Start a 7-day trial with the full platform — no credit card. Or talk to us about a Platinum or Enterprise rollout.