Summarize with AI
A good SaaS subheadline names what the product is and how it works, in one sentence of about 14 to 22 words. Picture the headline Ship faster with AI. Under it, App localization for iOS and Android: translates your string files into 24 languages and opens a pull request is a subheadline doing its job, and Transform how your team works is not.
This matters because the subheadline is the only line in the hero that is allowed to be fully specific. The headline is short and can be a promise. The button is two words. The sub is where a stranger learns what kind of company this is, and you are the one person who can never read it as a stranger, because you already know every word it leaves out.
Ship faster with AI, over a line that fits any company
Picture a localization tool for mobile app teams. This is an example, not a client. A developer connects the GitHub repo. The tool finds the iOS and Android string files, translates every new string into the 24 languages the team picked, and keeps the team's glossary, so a feature called Spaces is never translated into the German word for room. It flags any label that will spill out of its button on a small phone. Then it opens a pull request titled Add 37 new strings in 24 languages.
For the team that buys it, a release no longer waits a week for translations to come back. That is a real product with a clear job.
Now the homepage. The headline reads Ship faster with AI. The subheadline reads Transform how your team works. Two buttons of the same size sit under it, Get started and Book a demo. The image is a slowly turning globe with small flags floating around it. The words iOS, string file and pull request first appear in the third section, inside a card titled Built for developers. A visitor who reads the hero has learned that the company uses AI and wants teams to be faster. So does every other site they opened that morning.
On calls he says string files in the first minute
Watch the founder on a demo call. He opens by asking how long the team waits for translations before each release. Within a minute he has said string files, glossary and pull request, and the developer on the other end is nodding. Those three nouns are the whole pitch. None of them is in the hero.
He has rewritten the headline three times this quarter. It went from AI localization for modern teams, to Go global faster, to Ship faster with AI. Each version was shorter and punchier, and each time the subheadline under it stayed the same, because nobody has questioned it since launch week. When he reads the page, Transform how your team works feels complete. His head fills in the rest from two years of building the thing.
Why the second line, not the first, decides the visit
Most hero advice spends nine paragraphs on the headline and one on the subheadline, and that one usually says expand on the headline. That gets the job backwards. The headline has to be short, so it can only carry a promise or a category. The subheadline has room for a whole sentence, so it is the only place in the first screen where a visitor can find the category, the input and the output together.
So here is the claim most advice will not make. You can keep a vague headline if the subheadline is specific, and you cannot rescue a vague subheadline with any headline. Ship faster with AI is fine as a headline. It is a promise, and promises are what headlines are for. It only fails when the line under it is another promise.
Look at how Stripe's homepage splits the work. The headline is a short claim about financial infrastructure and growing revenue. The subheadline then names three concrete jobs: accept payments, handle business banking, and implement custom revenue models. A stranger who skips the headline still knows what Stripe does. That is the test your second line has to pass.
Three subheadline patterns, with before and after examples
There are three shapes that work under almost any SaaS headline. Each example below is invented for this post. Pick the shape that matches what a stranger is most confused about.
Pattern one: the category noun, then the mechanism. Use it when visitors cannot tell what kind of product this is. The shape is [category] for [platform or buyer]: [what it does to what].
- Before: Transform how your team works.
- After: App localization for iOS and Android: translates your string files into 24 languages and opens a pull request. That is 18 words, with the category in the first two.
Pattern two: the thing it replaces, then what you get and when. Use it when the category is obvious but the reason to switch is not. Picture an AI bookkeeping tool for small agencies.
- Before: The smarter way to close your books.
- After: Replaces the month-end reconciliation spreadsheet. Matches each bank deposit to its invoices and has the books ready to review by the second working day.
Pattern three: where it lives, then what it hands back. Use it when the product sits inside a tool the buyer already uses, so the setup is the selling point. Picture a data tool for sales teams.
- Before: Your data, supercharged.
- After: Works inside Google Sheets. Type a company name in column A and get headcount, funding stage and the head of sales in columns B to D.
Notice what the three rewrites share. Every one names something a visitor can picture: a string file, a bank deposit, a column. None of them uses the words smarter, transform or supercharged, because those words describe a feeling about the product rather than the product.
Eighteen words at 1440 pixels and at 375
Length is a layout decision as much as a writing one. On a desktop screen 1440 pixels wide, a subheadline set at about 20 pixels in a centred column around 640 pixels wide holds roughly 65 characters a line. Two lines is about 130 characters, which is 18 to 22 words. That is the ceiling. Past two lines, the sub starts to read like body copy and people skip it.
Then check the phone. At 375 pixels with a 16 pixel gutter on each side, the column is 343 pixels. At 17 or 18 pixels the same sentence wraps to about 38 characters a line, so an 18 word sub becomes four lines. Four is the limit. At five, the headline, the sub and the main button stop fitting in the first screen together, and the button is the one that drops out.
Do not fix this by hiding the sub on mobile or writing a shorter one for phones. The phone visitor needs the specific line more than anyone, because they are often reading in a gap between other things. Write one sentence that survives at 375, and cut the headline before you cut the sub.
What a borrowed subheadline costs a self-serve tool
Every visitor to that page was paid for, in ad spend, in a launch post, or in the founder's evenings on LinkedIn. The ones who leave from the hero cost the same as the ones who stay. Better traffic makes the waste bigger at the same ratio.
The visitors who stay can cost more. Some sign up thinking it is a widget that translates a marketing website. They paste in a paragraph, never connect a repo, and leave. They count as signups and never count as activated. Measured on SaaS and product-led companies, activation runs 20 to 40 percent for most products, and a ten point improvement typically drives a 15 to 25 percent increase in free-to-paid conversion. A subheadline that sends the right people in, and tells the wrong ones this is not for them, moves that number before anyone opens the product.
For an AI product the wrong signup is not free either. Each test translation costs inference. AI product builders average around 52 percent gross margin against 70 to 80 percent for traditional software, so there is less room to pay for people who were never going to use it.
Rewrite your subheadline this week in six steps
- Copy your headline and subheadline into a blank document. Cover the headline with your hand and read the sub alone. If it does not say what kind of product this is, it fails.
- Open the recordings of your last three demo calls and write down the nouns you say in the first minute. Those nouns are your raw material, not the adjectives on the page.
- Write three subs, one in each pattern above. Keep each between 14 and 22 words, and put the category noun or the replaced thing in the first five words.
- Paste each one into the live page using your browser's developer tools, and look at it at 1440 and at 375 pixels. Keep the ones that stay within two lines and four lines.
- Show the hero to five people who have never heard of you, using the five second test for a SaaS homepage. Ask what the product is and who it is for.
- Ship the winner and leave the headline alone for a month, so you know which line moved the numbers. If you would rather hand the whole first screen to a team, start with a ranking of landing page design agencies for AI devtools.
For how the subheadline sits with the product image and the button in the rest of the hero, see the guide to SaaS hero section design. This post covers only the second line, because that is the one founders rewrite last.
A subheadline is hard to write about your own product, since every vague phrase reads as complete to the person who knows the rest. Studio Maydit is a web and product design studio that builds in Framer, Webflow and custom code, and on a website the job is legibility: a stranger reading your hero should know what you are before the first scroll. Dualite, an AI app builder, reached 100,000+ users in seven months after design work supporting a repositioned ICP, when the site had to speak to the people who were actually signing up. A fixed-scope website project takes three to four weeks. If your subheadline has not changed since launch week, book a call and bring the hero as it stands.
