End a complete sentence with a period, unless it's a question. There are exceptions for working in lists.
Periods with lists
Whether to end a list item with a period depends on several factors, including the kind of list that the item appears in.
For details about how to use periods in lists, see the Capitalization and end punctuation section of the "Lists" page.
Periods with URLs
When a period immediately follows a URL or a file path, it can be hard to tell whether the period is part of the URL.
To indicate that the punctuating period isn't part of the URL, try one of the following techniques:
- Whenever possible, avoid putting URLs in text.
- Rewrite the sentence so that the URL isn't at the end of the sentence.
- Put the URL on a separate line from the text, omitting the final period.
If the URL is a link, it generally looks different from the surrounding text. For example, in most browsers, link text is blue by default. This formatting helps distinguish the URL from the period.
When you do put a period after a URL, don't leave any space between the last character of the URL and the period.
Periods with quotation marks
When a sentence ends with material inside quotation marks, place the period inside the quotation marks even if the period isn't part of the material inside the quotation marks.
Recommended: ... you might say "Fixed typo."
If the material inside the quotation marks ends with a question mark or an exclamation point, don't use a period.
Recommended: Children always ask "Why?"
For more information, see Quotation marks.
Periods with parentheses
If the last part of a sentence is contained inside parentheses, put the period after the closing parenthesis.
If the parentheses contain a complete sentence, put the period inside the parentheses.
Recommended: Your application could show a notification when a relevant file or folder has changed (even if that change occurs while your application isn't running).
Recommended: App Engine applications are easy to create, easy to maintain, and easy to scale. (With App Engine, there are no servers for you to maintain.)
For more information, see Parentheses.
Periods with headings
Don't end headings with periods.
For more information, see Headings.
Periods with numbers
Use a period to represent a decimal point. (Using a comma to separate the decimal part of a number is the editorial custom in some countries, but not in the US.)
For more information, see Numbers.
Periods with abbreviations
Put a period after a shortened word.
Don't put periods after the letters of an acronym or initialism.
For more information, see Abbreviations.
Spaces between sentences
Leave only one space between sentences.
Don't use exclamation points in text except when they're part of a code example.