Email subject line tester

Every subject line starts at 100. A Fix takes off 20 points, a Check 8 and a Tip 2. 85 and above is ready to send, 65 to 84 needs a few fixes, and under 65 should be rewritten.

The ten checks are length, how much of the subject line fits on a phone, personalisation, spam words, capital letters, punctuation and emoji, honesty, whether it sounds like a person wrote it, preview text and sender name.

The score measures how the subject line reads. Whether an email reaches the inbox also depends on your domain, your mailboxes and your list. The cold email spam checker covers the body copy and your domain setup.

The tester checks your subject line against the defaults Reachly writes to on every client campaign:

• 2 to 4 words, and 2 most of the time.
• Lower case, the way people type to colleagues.
• One variable tied to why you are writing: {{company_name}}, {{new_employee}} or {{tool}}.
• No pitch words, like "partnership", "opportunity" or "demo".
• No emoji, exclamation marks or fake "Re:" on a first email.
• The first line is the preview. Reachly opens with the trigger, like "I see you just hired {{new_employee}}".

A subject line like "{{new_employee}} onboarding" passes every check. More examples are in the cold email subject lines guide and the list of sales email subject lines.

On desktop, Gmail puts the sender, subject line and preview text on one line and cuts it at the edge of the window. A short subject line leaves more room for the preview text.

On a phone, the subject line gets its own line. The tester draws it on a 390 pixel wide phone screen and measures where your exact words get cut. That is usually 33 to 40 characters, and fewer when the words are wide.

The preview text comes from the first words of your email unless you set a preheader. In cold email there is no preheader, so your opening line shows straight after the subject. If it starts with "I hope this email finds you well", that is what the prospect reads before deciding to open.

Gmail sorts mail into tabs based on who sent it, how it was sent and what it says. Sales wording, percentages, prices, emoji and exclamation marks all make an email look like a promotion.

The tester only reads your wording, so it shows which tab your words point to. A cold email sent from a normal mailbox, in plain text with no tracking and no links, has a much better chance of reaching Primary than the same words sent from a marketing platform.

The big cold email studies agree on length and personalisation. They contradict each other on almost everything else, so treat any single rule with care.

Source: Belkins B2B cold email subject line statistics. All of Reachly's settings are being tested against live campaign data.

Type it into the subject line box above with your sender name and first line. The tester shows it in a Gmail inbox preview on phone and desktop, scores it out of 100 and tells you what to fix. To compare two versions in a live campaign, split your list and send each subject line to half, then compare replies, not opens.

For cold email, 2 to 4 words. That is short enough to read like a note from a colleague and to show in full on a phone. If you go longer, put the words that matter first in case the end gets cut.

Around 33 to 40 characters in the Gmail app on a typical phone, depending on the letters. Wide letters like "m" and "w" use more space than "i" and "l", which is why the tester measures your actual words instead of counting characters.

It can add to it. Spam trigger words, capitals, "!!" and fake "Re:" lines are all signals filters look at, but your domain setup, sending volume and how people react to your emails count for more. The tester flags the same spam words as Reachly's email spam checker.

Reachly writes them in lower case because it looks like a note from a colleague rather than a campaign. The studies are split on whether it changes open rates, so the tester treats Title Case as something to check, never as a fix.

Yes. There is no sign-up and no limit. Everything runs in your browser, so your subject line and preview text are never sent to Reachly or stored.