Regular Expressions 101

Non-Capturing Group(?:(\?=)|)

1st Alternative(\?=)

Group 1(\?=)

\?the literal ? (63₁₀ / 77₈ / 3F₁₆)

=the literal = (61₁₀ / 75₈ / 3D₁₆)

2nd Alternative — matches an empty string

Non-Capturing Group(?:(?:( |\n|\r\n)|)(?:( |\t)|)|)

1st Alternative(?:( |\n|\r\n)|)(?:( |\t)|)

Non-Capturing Group(?:( |\n|\r\n)|)

1st Alternative( |\n|\r\n)

Group 2( |\n|\r\n)

1st Alternative

the literal (32₁₀ / 40₈ / 20₁₆)

2nd Alternative\n

\na line-feed (newline) character (ASCII 10)

3rd Alternative\r\n

\ra carriage return (ASCII 13)

\na line-feed (newline) character (ASCII 10)

2nd Alternative — matches an empty string

Non-Capturing Group(?:( |\t)|)

1st Alternative( |\t)

Group 3( |\t)

1st Alternative

the literal (32₁₀ / 40₈ / 20₁₆)

2nd Alternative\t

\ta tab character (ASCII 9)

2nd Alternative — matches an empty string

Non-Capturing Group(?: |)

1st Alternative

the literal (32₁₀ / 40₈ / 20₁₆)

2nd Alternative — matches an empty string

Group 4(=)

=the literal = (61₁₀ / 75₈ / 3D₁₆)

Non-Capturing Group(?:[A-Za-z0-9].*|)

1st Alternative[A-Za-z0-9].*

Character Class[A-Za-z0-9]

A-Zone character from A (65₁₀) to Z (90₁₀) (case sensitive)

a-zone character from a (97₁₀) to z (122₁₀) (case sensitive)

0-9one character from 0 (48₁₀) to 9 (57₁₀)

.*any character (except for line terminators), repeated any number of times

2nd Alternative — matches an empty string

Group 5(\?(UTF|utf)\-8\?)

\?the literal ? (63₁₀ / 77₈ / 3F₁₆)

Group 6(UTF|utf)

1st AlternativeUTF

UTFthe literal text UTF (case sensitive)

2nd Alternativeutf

\-the literal - (45₁₀ / 55₈ / 2D₁₆)

8the literal 8 (56₁₀ / 70₈ / 38₁₆)

\?the literal ? (63₁₀ / 77₈ / 3F₁₆)

Group 7([A-Za-z0-9]\?)

Global pattern flags

g modifier: global. Finds all matches instead of stopping after the first

m modifier: multiline. Causes ^ and $ to match the start and end of each line, not only the start and end of the string

Detailed match information will be displayed here automatically.

Search reference

Regular Expression

(?:(\?=)|)(?:(?:( |\n|\r\n)|)(?:( |\t)|)|)(?: |)(=)(?:[A-Za-z0-9].*|)(\?(UTF|utf)\-8\?)([A-Za-z0-9]\?)

Test String
New

?=
	=?UTF-8?Q?
?=
 =?UTF-8?Q?
=3D?UTF-8?Q?
 =3D?UTF-8?Q?
=?UTF-8?Q?
 =?UTF-8?Q?
?= =?UTF-8?Q?

Regular Expression

Test StringNew

SubstitutionProcessing...

Test String
New

Substitution
Processing...