Want to get confident with number regex?
Start with exercises 01, 02, 06, 16, and 17. They cover digits only, exact length, signed integers, and decimals.
Guide: Regex for NumbersRegex Practice · 30 exercises
30 Regex Exercises with Solutions — Beginner to Advanced
Practice regex through short problems, real examples, and explained solutions. Start with numbers and simple patterns, then move into groups, JavaScript, lookarounds, and extraction.
How to practice Regex without memorizing syntax: Try each problem before opening the solution. Then test positive and negative cases in the Regex Tester. When it works, move into the 24-level game and keep your daily streak.
JavaScript Regex practice
Exercises 19, 20, 24, 28, and 29 cover capture, identifiers, named groups, and extraction — patterns that map naturally to JavaScript RegExp work.
Guide: JavaScript RegexBeginnerNumbers
01. Digits only
Match 12345; reject A123, 12-34, and an empty string.
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^\d+$
Anchors require the entire string to contain one or more digits.
BeginnerNumbers
02. Exactly four digits
Match 2026; reject 26 and 20260.
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^\d{4}$The {4} quantifier requires exactly four digits.
BeginnerText
03. ASCII letters only
Match RegexArena; reject Regex123 and regex-arena.
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^[A-Za-z]+$
This class covers ASCII letters; use Unicode-aware patterns when other alphabets matter.
BeginnerCodes
04. DEV prefix with optional hyphen
Match DEV-2026 and DEV2026; reject DE-2026.
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^DEV-?\d{4}$The ? makes the hyphen optional and \d{4} requires four digits.
BeginnerText
05. Simple slug
Match regex-arena and regex2026; reject spaces and duplicate hyphens.
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^[a-z0-9]+(?:-[a-z0-9]+)*$
Each additional block must be separated by a single hyphen.
BeginnerNumbers
06. Five to eight digits
Match 12345 and 12345678; reject shorter or longer values.
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^\d{5,8}$The {5,8} quantifier sets minimum and maximum length.
BeginnerLogs
07. Line starts with ERROR
Match ERROR connection lost; reject INFO ERROR.
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^ERROR\b
The start anchor fixes the position and closes the word.
BeginnerText
08. Repeated whitespace
Find one or more spaces, tabs, or line breaks so they can be replaced.
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\s+
\s represents whitespace and + captures a sequence.
BeginnerAlternation
09. Cat or dog, singular/plural
Match cat, cats, dog, and dogs.
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^(cat|dog)s?$
Alternation selects cat/dog and s? makes the plural optional.
BeginnerWeb
10. Hex color
Match #22aa77 and #FFFFFF; reject 22aa77.
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^#[0-9A-Fa-f]{6}$The hash is literal and the class requires six hexadecimal digits.
IntermediateUS format
11. ZIP code
Match 94105 and 94105-1234; reject 9410.
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^\d{5}(?:-\d{4})?$Five digits are required and the ZIP+4 suffix is optional.
IntermediateDates
12. DD/MM/YYYY date format
Match 11/10/2026; reject 2026-10-11.
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^\d{2}/\d{2}/\d{4}$This checks visual format, not whether the calendar date exists.
IntermediatePhone
13. Formatted phone number
Match (415) 555-1234; reject 415 555-1234.
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^\(\d{3}\) \d{3}-\d{4}$Literal parentheses must be escaped.
IntermediateEmail
14. Practical email shape
Match dev@example.com; reject dev@site and @example.com.
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^[\w.-]+@[\w.-]+\.[A-Za-z]{2,}$Useful for practice, but not a complete implementation of email standards.
IntermediateURL
15. HTTP or HTTPS URL
Match https://regexarena.com/en/; reject ftp://example.com.
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^https?://[\w.-]+\.[A-Za-z]{2,}(?:/.*)?$The optional s covers HTTP/HTTPS and the last group makes the path optional.
IntermediateNumbers
16. Signed integer
Match 42, -42, and +42; reject 4.2.
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^[+-]?\d+$
The sign is optional and the rest must contain digits only.
IntermediateNumbers
17. Decimal with dot or comma
Match 42, 42.50, and -42,50.
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^[+-]?\d+(?:[.,]\d+)?$
The decimal portion is optional and accepts a dot or comma.
IntermediateLogs
18. Log level and date
Match lines beginning with INFO, WARN, or ERROR followed by YYYY-MM-DD.
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^(INFO|WARN|ERROR)\s+\d{4}-\d{2}-\d{2}Alternation captures the log level and the second part requires the date.
IntermediateGroups
19. Capture email user and domain
In dev@example.com, capture dev as group 1 and example.com as group 2.
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^([\w.-]+)@([\w.-]+\.[A-Za-z]{2,})$Parentheses create capture groups that can be reused or inspected.
IntermediateJavaScript
20. Simple JavaScript identifier
Match userName, _cache, and $value; reject 2users.
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^[A-Za-z_$][\w$]*$
The first character has stricter rules; later characters may include word characters and $.
AdvancedLookahead
21. Positive lookahead
Capture DEV123 only when it is immediately followed by -OK.
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^DEV\d{3}(?=-OK$)The lookahead checks context without consuming -OK.
AdvancedLookahead
22. Negative lookahead
Match lowercase names except the exact word admin.
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^(?!admin$)[a-z]+$
The negative lookahead excludes the reserved value before testing the rest.
AdvancedLookbehind
23. Price without currency
In $ 150, capture only 150.
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(?<=\$ )\d+$
The lookbehind requires the prefix without including it in the match.
AdvancedGroups
24. Named group for a code
Capture DEV-2026 in a named group called code.
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(?<code>[A-Z]{3}-\d{4})Named groups make extracted data easier to understand in JavaScript and the visualizer.
AdvancedBackreference
25. Repeated word
Find the the or regex regex; reject regex arena.
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\b(\w+)\s+\1\b
requires the second word to equal what group 1 captured.
AdvancedValidation
26. Password with uppercase and digit
Require at least 8 characters, one uppercase letter, and one digit, using letters and digits only.
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^(?=.*[A-Z])(?=.*\d)[A-Za-z\d]{8,}$Two lookaheads verify requirements before the allowed character set is validated.
AdvancedFiles
27. Image extension
Match files ending in jpg, jpeg, png, or webp using the i flag.
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^.+\.(?:jpe?g|png|webp)$
The non-capturing group collects extensions and jpe?g covers jpg/jpeg.
AdvancedGroups
28. Date with named groups
Capture day, month, and year from 11/10/2026 using named groups.
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^(?<day>\d{2})/(?<month>\d{2})/(?<year>\d{4})$Each date part becomes available by name for later extraction.
AdvancedURL
29. Capture host and path
For an HTTP/HTTPS URL, capture the host as host and the optional path as path.
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^https?://(?<host>[\w.-]+\.[A-Za-z]{2,})(?<path>/.*)?$Named groups split useful parts while still checking the overall format.
AdvancedBoss
30. Context window
Capture DEV-2026 only after ID: and before ;OK.
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(?<=ID:)(?<code>[A-Z]{3}-\d{4})(?=;OK$)Combine lookbehind, a named group, and lookahead in one challenge.
Keep practicing
Turn practice into a habit: test patterns, play missions, and use smart review to reinforce weaker concepts.