Regex Lab is the fastest way to build, test, and understand regular expressions on iPhone and iPad. Whether you're a seasoned developer hunting down a tricky pattern or a student learning regex for the first time, Regex Lab turns every keystroke into instant, color-coded feedback so you can see exactly what your pattern matches — and why. KEY FEATURES • LIVE TESTER — Type your pattern and test string side-by-side. Matches highlight in real time with color-coded backgrounds, plus full capture-group inspection for every match. Jump between matches with prev/next navigation. • PATTERN EXPLAINER — Tap "Explain" and Regex Lab breaks your pattern down token by token. Anchors, quantifiers, character classes, groups, lookaround, escape sequences, and backreferences are each annotated with a plain-English description. • REPLACE TOOL — Build search-and-replace expressions with full $0, $1, $2… capture-group references. See input and output side-by-side with a live replacement counter, plus one-tap copy of the result. • SNIPPETS LIBRARY — Save patterns with names, notes, categories, and favorites. Search by name or pattern, filter by category, swipe to copy or delete, and load any snippet straight into the tester. Long-press for a quick-action menu. • BUILT-IN TEMPLATES — Twelve battle-tested patterns ready to use: email addresses, HTTP/HTTPS URLs, IPv4 addresses, US phone numbers, ISO 8601 dates, credit cards, hex colors, HTML tags, whitespace, whole words, numbers, and URL slugs. • REGEX CHEATSHEET — A searchable, categorized reference for anchors, quantifiers, character classes, groups, lookaround, special characters, and flags. Every symbol is tap-to-copy. • FLAGS & OPTIONS — Toggle case-insensitive (i), multiline (m), dot-matches-newlines (s), and extended syntax (x) and watch your matches update instantly. • POWERED BY NSREGULAREXPRESSION — Built on Apple's native engine, so what you test in Regex Lab behaves identically in your Swift, Objective-C, and Foundation code. DESIGNED FOR iOS • Native SwiftUI experience with full Dark Mode support • Adaptive layouts for iPhone and iPad • Monospaced typography tuned for code • 100% offline — no accounts, no analytics, no tracking Whether you're parsing log files, validating user input, writing migrations, building a scraper, or just trying to remember what \b does — Regex Lab keeps your regex toolbox in your pocket. Download Regex Lab today and write your next regular expression with confidence. Thank you for your support. Please visit nitrio.com for more apps for your iOS devices.