Regular Expressions 101

Pro

Group 1(\b(?:M{1,4})?(?:CM|CD|D?C{1,3})?(?:XC|XL|L?X{1,3})?(?:IX|IV|V?I{1,3})?\b)

\ban ASCII word boundary

Non-Capturing Group(?:M{1,4})?

?repeats the group contents below at most once:

M{1,4}the literal M (77₁₀ / 115₈ / 4D₁₆) (case sensitive), repeated between 1 and 4 times

Non-Capturing Group(?:CM|CD|D?C{1,3})?

?repeats the group contents below at most once:

1st AlternativeCM

CMthe literal text CM (case sensitive)

2nd AlternativeCD

CDthe literal text CD (case sensitive)

3rd AlternativeD?C{1,3}

D?optionally matches the literal D (68₁₀ / 104₈ / 44₁₆) (case sensitive)

C{1,3}the literal C (67₁₀ / 103₈ / 43₁₆) (case sensitive), repeated between 1 and 3 times

Non-Capturing Group(?:XC|XL|L?X{1,3})?

?repeats the group contents below at most once:

1st AlternativeXC

XCthe literal text XC (case sensitive)

2nd AlternativeXL

XLthe literal text XL (case sensitive)

3rd AlternativeL?X{1,3}

L?optionally matches the literal L (76₁₀ / 114₈ / 4C₁₆) (case sensitive)

X{1,3}the literal X (88₁₀ / 130₈ / 58₁₆) (case sensitive), repeated between 1 and 3 times

Non-Capturing Group(?:IX|IV|V?I{1,3})?

?repeats the group contents below at most once:

1st AlternativeIX

IXthe literal text IX (case sensitive)

2nd AlternativeIV

IVthe literal text IV (case sensitive)

3rd AlternativeV?I{1,3}

V?optionally matches the literal V (86₁₀ / 126₈ / 56₁₆) (case sensitive)

I{1,3}the literal I (73₁₀ / 111₈ / 49₁₆) (case sensitive), repeated between 1 and 3 times

\ban ASCII word boundary

Global pattern flags

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

Detailed match information will be displayed here automatically.

25 tokens

(\b(?:M{1,4})?(?:CM|CD|D?C{1,3})?(?:XC|XL|L?X{1,3})?(?:IX|IV|V?I{1,3})?\b)

New

VII
CMXL
XII
XVII
IV
MMMIII
MXI
MXIV
MM
MC
MM
I
VI
MX

VII
CMXL
XII
XVII
IV
MMMIII
MXI
MXIV
MM
MC
MM
I
VI
MX