Regex Tester

Debug JavaScript-style regexes with safe presets, clearer match summaries, and explicit share links for the exact state you want to review.

Regex Inputs

Pattern

/ /

g Global i Case Insensitive m Multiline s Dotall

Sample Text

https://comutil.com/regex

Workflow Summary Ready

Status Load a preset or enter a pattern to start debugging.

Current preset No preset loaded

Active flags g

Match count 0

First match Not found yet

First position Not found yet

Context Context will appear here after the first match.

Capture Groups

Capture groups from the first match will appear here.

Highlighted Matches

Matches will be highlighted here...

Match List

Matches will be listed here...

Use the live regex tester, then continue the automation review

Stay on this page for the active match summary, then jump into the matching guide or the related cron, Markdown, and diff explainers when the task expands.

Read the regex guide Open Automation/Text Ops hub

Automation/Text Ops hub

Return to the cluster chooser for cron, regex, Markdown, and diff workflows.

Cron debugging guide

Switch to cron when the automation issue is schedule timing, not pattern matching.

Markdown preview guide

Capture the final regex notes in a browser-first document once the pattern is clear.

Diff review guide

Compare old and new pattern revisions when the review is about change scope.

Unix Timestamp / Epoch Converter

Need to turn a matched epoch value into a readable date?

Debugging Presets

Email extraction

Start with a support-style message and confirm the regex catches every mailbox without missing plus tags.

Request log parser

Inspect a small HTTP log excerpt and capture method, path, and status code in one pass.

SemVer release tags

Check version strings in release notes and surface capture groups for major, minor, patch, and prerelease values.

Scan copied logs or tickets for URLs before you move them into another debugging tool.

Debugging Workflow

1. Load a preset Start with a safe example so you can confirm the shape of the regex before using real data.

2. Adjust flags Turn on global, multiline, or case-insensitive behavior while watching the summary update immediately.

3. Inspect groups Use the first-match summary and capture-group panel to verify exactly what your groups return.

4. Share explicitly Refresh or copy the URL only when you want to keep or send the current state.

What is Regex?

Regular expressions (regex) are sequences of characters that define search patterns. They're used for string matching, searching, and text manipulation. Regex is supported in virtually all programming languages and many text editors. While powerful, regex syntax can be complex and requires practice to master.

Regex Syntax Basics

Regex uses literal characters and metacharacters. Common metacharacters include: . (any character), * (zero or more), + (one or more), ? (optional), ^ (start), $ (end), [] (character class), () (grouping), | (alternation). Escape special characters with backslash.

Common Use Cases

Validating email addresses and phone numbers
Extracting data from text (web scraping)
Search and replace in code editors
Log file analysis and parsing
Input sanitization and validation

Common Patterns

Email ^[\w.-]+@[\w.-]+\.\w+$

URL https?://[\w.-]+(?:/[\w.-]*)*

Phone (US) \d{3}-\d{3}-\d{4}

IPv4 \d{1,3}\.\d{1,3}\.\d{1,3}\.\d{1,3}

Frequently Asked Questions

Why doesn't my regex work in different languages?

Regex flavors vary between implementations. JavaScript, Python, and PCRE have subtle differences in supported features. Always test your regex in the target environment.

How do I make regex more efficient?

Avoid catastrophic backtracking by using specific character classes instead of .*, use anchors (^ and $), and prefer possessive quantifiers when available. Profile complex patterns with large inputs.