Guides
Practical how-tos for developers, marketers and everyday computer tasks — each one uses free devpack tools you can open alongside it.
FeaturedHow to Compress Images Without Losing QualityMake photos and screenshots smaller for email, forms and websites: resize first, pick the right format and quality, and hit a KB limit without visible loss.Read the guide
How to Decode and Debug a JWTRead a JSON Web Token’s header and claims, find why it’s rejected — expired, wrong audience, bad signature — and the security mistakes to avoid.
Regex for Email, URL and Phone Number ValidationPractical regular expressions for emails, URLs and phone numbers, why “perfect” patterns don’t exist, and when to use a parser instead of regex.
Cron Expressions Explained: 15 Real Schedules and the Time Zone TrapsRead and write cron expressions with confidence: the five fields, 15 copy-paste schedules, the day-of-month vs day-of-week trap and time zones in CI.
How to Fix CORS ErrorsWhy the browser blocks your request, how to read the CORS error, and the right headers for Express, Nginx and Vercel — including preflight and cookies.
301 vs 302 vs 307 vs 308: Which Redirect to UseWhen to use each HTTP redirect, how they affect SEO and form posts, how to avoid redirect chains and loops, and copy-paste rules for Apache, Nginx and Vercel.
Generate TypeScript Types from JSON — the Right WayTurn API JSON into TypeScript interfaces, handle optional vs nullable fields and unions, and add runtime validation with JSON Schema so types match reality.
How to Set Up GA4 with Google Consent Mode v2Install Google Analytics 4 with Consent Mode v2 correctly: default-denied consent, updating it from your cookie banner, and how to verify it really works.
HTTP Security Headers Checklist (with Copy-Paste Configs)The security headers every site should send — HSTS, CSP, nosniff, frame-ancestors, Referrer-Policy, Permissions-Policy — with safe values and configs.
How to Merge, Split and Compress PDF FilesCombine PDFs, pull out or remove pages, shrink a large scan to email it and turn phone photos into a PDF — free, in your browser, no uploads.
The Pomodoro Technique: How to Actually Make It WorkHow the Pomodoro Technique works, what to do in breaks, how to handle interruptions, when to change the 25-minute length, and how to track your sessions.
How to Test Your Webcam and Microphone Before a Video CallCheck your camera and microphone in the browser, fix “camera not found” and permission errors on Windows and Mac, and sound and look better on calls.
How to Create a Strong Password and Check If It Was LeakedWhat really makes a password strong, why length beats symbols, how passphrases and password managers help, and how to check for breaches safely.
UTM Parameters Explained: Track Every Campaign in GA4What UTM parameters are, how to name source, medium and campaign so GA4 groups them correctly, where not to use them, and how to track QR codes and print.
How to Write Title Tags and Meta Descriptions That Get ClicksWrite title tags and meta descriptions people click: pixel length limits, a simple formula, avoiding rewrites and duplicates, and Open Graph tags.
How to Test a Used Laptop Before You Buy ItA 15-minute checklist for buying a used laptop: screen dead pixels, keyboard and touchpad, battery health, real specs, storage, camera, mic and account locks.