Test regular expressions against sample strings in the browser. See matches, groups, and flags without deploying code—helpful when debugging validators, log par
Overview
Test JavaScript regular expressions against sample strings. See matches, capture groups, and flags locally—no deploy, no signup. Free in your browser on Case…
What this page covers
Test regular expressions against sample strings in the browser. See matches, groups, and flags without deploying code—helpful when debugging validators, log parsers, and rewrite rules.
Quick answer
Test JavaScript regular expressions against sample strings. See matches, capture groups, and flags locally—no deploy, no signup. Free in your browser on Case… Use it in a browser with no account required, then review the output before publishing or shipping.
About Regex Tester
Test regular expressions against sample strings in the browser. See matches, groups, and flags without deploying code—helpful when debugging validators, log parsers, and rewrite rules.
How to Use Regex Tester
Enter your regex pattern in the pattern field. Paste the test string in the input area. Toggle flags (global, case-insensitive, multiline) as needed. Review match highlights and captured groups, then refine the pattern.
When to Use Regex Tester
Form validation: Prototype email, phone, and slug patterns before shipping. Data cleaning: Extract IDs or dates from semi-structured logs. SEO redirects: Test path patterns before adding server rules. Interviews & learning: Experiment with quantifiers and lookaheads safely.
Why Use This Regex Tester?
Regex errors often surface only on edge-case production data. A live tester shortens the feedback loop compared to redeploying backend validators.
How to use this tool
- Enter your regex pattern in the pattern field.
- Paste the test string in the input area.
- Toggle flags (global, case-insensitive, multiline) as needed.
- Review match highlights and captured groups, then refine the pattern.
Getting started
Test regular expressions against sample strings in the browser. See matches, groups, and flags without deploying code—helpful when debugging validators, log par
Privacy and local processing
Regex Tester Tool runs in your browser on Case Modify. Typical conversions do not upload your pasted text to our servers for processing.
You still share data with your browser vendor and network as with any website; see our privacy policy for analytics and ads. When you work with secrets, credentials, or personal data, review the output locally before you publish or send it.
Details: privacy policy.
Before you publish
Unicode styling, formatted code, and converted units can look correct in the preview but fail in the target app because of font support, line breaks, or platform limits.
Test a short sample in the destination (bio field, IDE, CMS, or spreadsheet) before you paste a long block.
Workflow tips: how Case Modify works, documentation hub.
Limits to keep in mind
Free browser utilities excel at quick edits, classroom exercises, and copy-paste formatting. They are not a replacement for licensed design software, production build pipelines, or compliance review.
When a platform rejects styled Unicode, fall back to plain ASCII from a case converter or remove formatting before you submit final copy.
Frequently asked questions
Which regex flavor does this use?
JavaScript RegExp semantics (ES2018+ features where supported by your browser). Server engines like PCRE may differ slightly—re-test before production.
Related Tools
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JSON Formatter: Pretty-print messy JSON, catch syntax issues, or minify for production—all in one free online tool.
Slugify URL Generator: Paste a headline, get a clean slug for blogs and SEO.
URL Encode & Decode: Fix broken links and special characters in URLs.