prefer_single_quotes

Only use double quotes for strings containing single quotes.

DO use single quotes where they wouldn't require additional escapes.

That means strings with an apostrophe may use double quotes so that the apostrophe isn't escaped (note: we don't lint the other way around, ie, a single quoted string with an escaped apostrophe is not flagged).

It's also rare, but possible, to have strings within string interpolations. In this case, it's much more readable to use a double quote somewhere. So double quotes are allowed either within, or containing, an interpolated string literal. Arguably strings within string interpolations should be its own type of lint.

BAD:

useStrings(
    "should be single quote",
    r"should be single quote",
    r"""should be single quotes""")

GOOD:

useStrings(
    'should be single quote',
    r'should be single quote',
    r\'''should be single quotes\''',
    "here's ok",
    "nested \${a ? 'strings' : 'can'} be wrapped by a double quote",
    'and nested \${a ? "strings" : "can be double quoted themselves"}');

The prefer_single_quotes rule is incompatible with the following rules:

• prefer_double_quotes

To enable the prefer_single_quotes rule, add prefer_single_quotes under linter > rules in your analysis_options.yaml file:

linter:
  rules:
    - prefer_single_quotes

If you're instead using the YAML map syntax to configure linter rules, add prefer_single_quotes: true under linter > rules:

linter:
  rules:
    prefer_single_quotes: true

Unless stated otherwise, the documentation on this site reflects Dart 3.6.0. Page last updated on 2025-01-27. View source or report an issue.