Test whether a string contains a substring matching the pattern:

Give a list of strings as input:

Use the operator form of StringFreeQ:

Use the operator form to select strings:

Use string patterns:

Use a regular expression:

Mix regular expressions and string patterns:

Use pattern matching for dates:

Test for occurrences of either pattern:

StringFreeQ automatically threads over lists of strings:

Check whether a biomolecular sequence is free of a particular substring:

Use a wildcard in the pattern compared against a biomolecular sequence:

The "N" is a degenerate letter only in biomolecular sequences:

Check for the absence of literal degenerate letters using Verbatim:

Circular sequences support wraparound checks:

Pick all the lines that contain a substring that matches the pattern:

Line numbers with corresponding texts that contain "noon" or "day of":

StringFreeQ threads over lists of strings in the first argument:

StringFreeQ["string",{patt₁,patt₂,…}] is equivalent to StringFreeQ["string",Alternatives[patt₁,patt₂,…]]:

StringContainsQ["string",patt] is equivalent to !StringFreeQ["string",patt]:

Use StringMatchQ to check whether a whole string matches a pattern:

StringFreeQ generally returns False when StringMatchQ is True:

Use StringStartsQ to check whether the start of a string matches a pattern:

StringFreeQ returns False whenever StringStartsQ is True:

Use StringEndsQ to check whether the end of a string matches a pattern:

StringFreeQ returns False whenever StringEndsQ is True:

Get the starting and ending positions where a substring occurs by using StringPosition:

Use StringCases to extract substrings matching a given pattern: