Write all numbers numerically, even numbers under 10. But if a number starts a sentence, spell it out. (If it's a really big number like 5,678, rewrite the sentence so it doesn't start with the number.)
If the number is over 999, include a comma. But don't include a comma for XP or other currency totals in the product.
Pull from this set of emoji that test well.
Emoji can be placed in either the title (the top line) or the body (the next line), either at the beginning or end of copy. Your call!
Keep it to one emoji. (Unless 2+ makes more sense for the message; see bottom example)
Not every push notification needs an emoji. Omit emoji ~half the time so they don't lose their impact.
Pull from this set of emoji that test well.
Follow this order: emoji, space, beginning of subject line copy.
A/B test a few subject lines, some with emoji and some without, to determine what gets sent to the full list.
We can be looser with the rules on Twitter, Instagram, and (less frequently used) Facebook. Use the emoji that match the message, whichever and however many make sense.
Emoji are super useful. They convey information. They grab attention. But a little emoji go a long way.
Don't punctuate headlines, except with an exclamation point.
Don't punctuate subheads, unless with an exclamation point. If it's a multi-sentence subhead, punctuate each sentence.
Never use punctuation in a button.
Punctuation marks help us break information into readable chunks. They also dictate the tone of our content! (Like so!) We have some hard-and-fast rules for which punctuation marks we use where....and which we really, really try to avoid.
Periods go inside quotation marks. Always follow a period with one space, not two.
Use a hyphen (-) to join two words, usually to create a compound adjective. Note: Don't hyphenate "x day streak." Don't use a hyphen when the first word of a compound adjective ends in -ly.
Use an en dash (–), with no space on either side, to indicate a range. Think of – as replacing the words "through" or "to."
Avoid em dashes (—). It's more Duolingo style to have two sentences than one long sentence broken up with a dash. If you must use an em dash, put a space on either side.
There are three — yes, three — kinds of dashes. We mostly use hyphens and en dashes.
If the copy following a colon is a fragment, don't capitalize the first word. If it's a complete sentence, capitalize!
Use the serial comma (a.k.a. Oxford comma).
We don't use ellipses frequently...but when we do, there isn't a space on either side... But if the ellipsis ends the sentence, add a space.
Instead of a semicolon, use an em dash. Even better: Break long, two-part sentences into two simple sentences.
When a singular word ending in s, x, or z has a possessive, put an s after the apostrophe.
When writing in English, periods and commas go inside quotation marks. Everything else (!, ?, ;) goes outside quotation marks, unless it's part of the quoted material. Note that other languages have differing conventions for punctuation marks, and we observe them when copy is localized.
Include a comma before a quote if the words before it describe the writing or saying of the quote.
Simple rules to get statements right.
Avoid using & to replace "and" in copy. One exception is ads with a low character count — but when there is space to write out "and," it is more user-friendly.
Formatting is like visual design for copy. These guidelines aren't grammatical rules, but rather how we treat these situations at Duolingo.
Put button copy in all caps.
Use sentence case for headers and subheads.
Use sentence case for blog post titles and page titles.
Use title case for video titles. (This is the norm on YouTube.)
Use title case for titles of stories.
We minimize capitalization in an effort to make our product and brand as approachable as possible. That's not to say that everything is lowercase — we do put button copy in ALL CAPS, and most feature names (like Stories) are capitalized.
See Should I capitalize it? for guidelines on specific words.
Before a list, conclude copy with a colon. Don't capitalize or punctuate for lists consisting of phrases or single words.
My favorite fruits are:
Capitalize the first word of a list item if it's a complete sentence, and end it with punctuation.
People use Duolingo for different reasons:
All list items should be formatted identically. So if one fragment, all fragments. If one sentence, all sentences.
Bold text to refer to UI elements or actions.
Italicize titles of books, magazines, films, and music albums. Put quotation marks around song titles and article titles. (This may never come up, but it's a good rule to know.)
Leave off the http:// and www., and put the rest of the URL in lowercase. Put email addresses in all lowercase.
Welcome to the nitty gritty of grammar! Forget what you learned in school: Every brand has its rules for certain word types. And these are ours.
Contractions are okay and encouraged. Use them when they make a sentence read more naturally. (In some cases, not using contractions is a strong way to get something important across.)
It's okay to start a sentence with a conjunction (and, but, or).
It's okay to end a sentence with a preposition (to, for, of, with, etc.) if it reads more naturally.
Guidelines for the miscellaneous characters and symbols that work their way into copy.
Hyphens only, no parentheses.
Put the dollar sign or other currency symbol in front of the amount. For even amounts, omit .00. If less than a dollar, write x cents.
Use the % symbol instead of writing out percent.
Write the numeral and then am or pm, with a space between. If the time is on the hour, write it as :00. Midnight and noon are neither am nor pm, so write midnight and noon on their own.
Consult these charts before hitting the Shift key or Caps Lock.
Generally speaking, we capitalize things that are particular to Duolingo, whether that's an achievement name or a feature type.
We like to keep headers, subject lines, and most things lowercase to maintain Duolingo's feeling of approachability.