# Regex Playground > A hands-on developer playground for API request testing, regex, JWT decoding, cron, JSON and mock responses — everything runs in your browser, nothing gets logged. Every tool and article on Regex Playground is free to use — no sign-up required. The links below are the primary, canonical resources on this site. ## Tools - [Engagement Rate Calculator](https://smttooling.xyz/tool/engagement-rate-calculator/): Why Your Follower Count Is Lying to You There's a quiet obsession in the creator economy, and it has nothing to do with follower counts. Brand manage… - [Brand Voice Analyzer](https://smttooling.xyz/tool/brand-voice-analyzer/): When Your Brand Sounds Like Three Different People: A Real Look at Brand Voice Analyzer Last year, a small SaaS company I consulted for had a problem… - [Email Subject Line Generator](https://smttooling.xyz/tool/email-subject-line-generator/): What an Email Subject Line Generator Actually Does (and Why Developers Care) If you've ever spent twenty minutes staring at a blank subject line fiel… - [YouTube Description Generator](https://smttooling.xyz/tool/youtube-description-generator/): What a YouTube Description Generator Actually Does Under the Hood Most people treat the YouTube description field as an afterthought — a place to dum… - [Pinterest Pin Description](https://smttooling.xyz/tool/pinterest-pin-description/): What the Pinterest Pin Description Tool Actually Does (And Why Developers Care) If you've ever tried to automate Pinterest content at scale — bulk-pi… - [Facebook Ad Copy Generator](https://smttooling.xyz/tool/facebook-ad-copy-generator/): What Is a Facebook Ad Copy Generator, and Why Should Developers Care? Most discussions about Facebook Ad Copy Generators focus on marketers. But deve… - [TikTok Script Writer](https://smttooling.xyz/tool/tiktok-script-writer/): Why TikTok Script Writers Have Become a Developer's Secret Weapon If you've ever stared at a blank page trying to figure out how to turn a 30-second… - [LinkedIn Post Generator](https://smttooling.xyz/tool/linkedin-post-generator/): Why LinkedIn Post Generators Have Become Developer Tools Worth Taking Seriously There is a persistent myth in developer circles that writing about yo… - [Twitter Thread Generator](https://smttooling.xyz/tool/twitter-thread-generator/): What Is a Twitter Thread Generator and Why Developers Love It If you've ever spent an hour manually breaking a long technical post into 25 numbered t… - [Instagram Caption Generator](https://smttooling.xyz/tool/instagram-caption-generator/): The Blank Caption Problem That Nearly Broke My Content Strategy It was a Tuesday evening, and I had seventeen product photos queued up for a client's… - [Regex Tester & Debugger](https://smttooling.xyz/tool/regex-tester-debugger/): Free online Regex Tester & Debugger — real-time match highlighting, capture group breakdown, JS/PCRE/Python flavor support, and inline flag toggles. … - [Cron Expression Generator](https://smttooling.xyz/tool/cron-expression-generator/): Free online Cron Expression Generator. Build cron schedules visually, translate any 5- or 6-field cron expression into plain English, and preview the… - [JWT Decoder & Verifier](https://smttooling.xyz/tool/jwt-decoder-verifier/): Free browser-based JWT decoder and verifier. Decode headers, payloads, inspect claims and expiry, verify HS256/RS256 signatures with your secret or p… - [Cron Expression Explainer](https://smttooling.xyz/tool/cron-expression-explainer/): Free online cron expression explainer — paste any cron string, get an instant human-readable description and upcoming run timestamps in your timezone… - [Regex Cheatsheet & Builder](https://smttooling.xyz/tool/regex-cheatsheet-builder/): Free regex builder and cheatsheet. Click common patterns like email, IP address, and date to construct regex. Searchable reference for tokens, anchor… - [HTTP API Request Tester](https://smttooling.xyz/tool/http-api-request-tester/): Free browser-based HTTP API Request Tester. Send GET, POST, PUT, DELETE requests with custom headers, query params, and JSON bodies. Inspect status, … - [JSON Formatter & Validator](https://smttooling.xyz/tool/json-formatter-validator/): Free online JSON Formatter & Validator. Beautify, minify, and validate JSON with error line pointers and a collapsible tree view. Perfect for debuggi… - [Regex Replace Playground](https://smttooling.xyz/tool/regex-replace-playground/): Free online Regex Replace Playground — test find-and-replace patterns with capture group backreferences and named groups, preview every substitution … - [Base64 Encoder & Decoder](https://smttooling.xyz/tool/base64-encoder-decoder/): Free online Base64 encoder and decoder. Supports standard Base64, URL-safe Base64, and JWT segment inspection. Works entirely in your browser with no… - [Timestamp & Cron Converter](https://smttooling.xyz/tool/timestamp-cron-converter/): Free online tool to convert Unix timestamps to human dates across timezones and find the next cron job fire times. Instant, client-side, no login req… - [API Mock Response Builder](https://smttooling.xyz/tool/api-mock-response-builder/): Build and preview fake API endpoints with custom JSON body, HTTP status codes, response headers, and artificial delays to test client error handling … - [URL Parser & Query Builder](https://smttooling.xyz/tool/url-parser-query-builder/): Free online URL parser and query builder. Decompose any URL into protocol, host, path, and query params. Edit and rebuild with correct percent-encodi… ## Articles - [Why 2026 Is the Year to Switch to g100.us for Business Numbers](https://smttooling.xyz/why-switch-g100us-2026/): Why switch to g100.us in 2026: one number for calls, SMS & WhatsApp, 100+ countries, instant activation, no contracts. See how g100.us compares. - [Business Number Checklist: What Every Owner Should Demand](https://smttooling.xyz/business-number-checklist-g100us/): A real business number checklist — unified channels, instant activation, flat pricing, no contracts — with g100.us measured against every item. - [Your Questions About Regex Flags Answered: g, i, m, s, u, and y](https://smttooling.xyz/regex-flags-answered/): Answers to the most common regex flag questions: what g, i, m, s, u, and y actually do, with short code examples for each toggle. - [Decoding a JWT by Hand: What's Really Inside That Token](https://smttooling.xyz/decoding-jwt-by-hand/): Manually decode every segment of a JWT using only your terminal. Understand the header, claims, and signature — and where the security guarantees act… - [Cron Alternatives in 2026: systemd Timers, Quartz, and Cloud Schedulers](https://smttooling.xyz/cron-alternatives-2026/): A data-driven survey of cron alternatives in 2026: systemd timers, Quartz, AWS EventBridge, GCP Cloud Scheduler, and more for teams scaling beyond a … - [Catastrophic Backtracking: The Regex Bug That Took Down a Service](https://smttooling.xyz/catastrophic-backtracking-regex-outage/): How a single nested quantifier in a regex caused a 6-minute auth outage — a detailed ReDoS post-mortem with the fix and safeguards we added afterward. - [The Anatomy of an HTTP Request: Headers, Methods, and Status Codes](https://smttooling.xyz/anatomy-of-http-request/): Dissect every part of an HTTP request and response — methods, headers, JWT auth, status codes — so API testers know exactly what each field controls. - [How to Validate Email Addresses With Regex (and When Not To)](https://smttooling.xyz/validate-email-addresses-regex/): Learn a simple, permissive email regex that works in production, why strict patterns reject valid addresses, and why a confirmation email beats any r… - [JWT vs Session Cookies: Which Auth Strategy Should You Choose?](https://smttooling.xyz/jwt-vs-session-cookies-auth/): JWT vs session cookies: a practical comparison covering scalability, revocation, XSS/CSRF tradeoffs, and a real decision framework for your auth arch… - [Why My Cron Job Ran at the Wrong Time (and How Timezones Tricked Me)](https://smttooling.xyz/cron-job-wrong-time-timezone/): A cron job fired at the wrong time because of UTC vs local timezone assumptions. Here's the debugging story and the fixes that actually work. - [Stop Believing These 6 Myths About Regular Expressions](https://smttooling.xyz/myths-about-regular-expressions/): Six regex myths busted: catastrophic backtracking, HTML parsing, readability, performance, and cross-engine differences — with practical guidance for… - [JWT Security: 7 Mistakes That Leave Your API Wide Open](https://smttooling.xyz/jwt-security-mistakes-api-vulnerable/): Audit your JWT implementation for 7 common security mistakes: alg:none attacks, weak secrets, missing expiry checks, and more. With real fixes. - [Cron Syntax Explained: What Those Five Asterisks Actually Mean](https://smttooling.xyz/cron-syntax-five-asterisks-explained/): Learn what cron's five fields actually mean — minute, hour, day-of-month, month, day-of-week — with plain-English examples for complete beginners. - [Mastering Regex Lookaheads and Lookbehinds Without the Headache](https://smttooling.xyz/mastering-regex-lookaheads-lookbehinds/): Learn regex lookaheads and lookbehinds with concrete before/after examples. Fix password validation, parse API logs, and stop misusing zero-width ass… ## About & Policies - [About Us](https://smttooling.xyz/about-us/) - [Contact Us](https://smttooling.xyz/contact-us/) - [Terms of Service](https://smttooling.xyz/terms-of-service/) - [Disclaimer](https://smttooling.xyz/disclaimer/) - [Privacy Policy](https://smttooling.xyz/privacy-policy/) ## Notes - Full URL list: https://smttooling.xyz/sitemap.xml - Content is original and maintained by Regex Playground. Attribution is appreciated when cited.