Guides
Short explanations of the things developers actually look up, written to answer the question properly rather than pad it out. Each one ends at a free tool that does the work in your browser.
How to Center a Div in CSS: Every Method and When to Use It
Center anything in CSS with grid, flexbox, margin auto or absolute positioning. What each method does, the one gotcha behind most failures, and which to pick.
4 min readUses the Flexbox Playground
Why One Box Shadow Looks Cheap, and How Layered Shadows Fix It
A single box shadow rarely looks real. Learn the two-shadow technique design systems use, why negative spread matters, and how to animate shadows without the cost.
3 min readUses the Box Shadow Generator
CSS Gradients Without the Muddy Grey Band in the Middle
Why gradients between two bright colours turn grey in the middle, and three fixes: a middle stop, closer hues, or interpolating in oklch.
3 min readUses the CSS Gradient Generator
Why Is My JSON Invalid? The Six Errors Behind Almost All of Them
Most invalid JSON is perfectly valid JavaScript. The six mistakes that cause nearly every JSON parse error, with before and after examples and how to find them fast.
3 min readUses the JSON Formatter
How to Read a JWT, and Why You Should Never Put Secrets in One
A JSON Web Token is encoded, not encrypted, so anyone can read it. How to decode the header and payload, what the standard claims mean, and the security traps to avoid.
4 min readUses the JWT Decoder
How Long Should a Password Be? Entropy Explained Simply
Why length beats complexity, with the actual numbers. What password entropy measures, how many bits is enough, and the bigger risk most people ignore.
4 min readUses the Password Generator
How to Make a QR Code That Never Expires
Why many free QR codes stop working, the difference between static and dynamic codes, and how to make one that scans forever and still gets you analytics.
4 min readUses the QR Code Generator
Meta Title and Description: How Long, and What Actually Matters
How long a title tag and meta description should be, why Google measures pixels not characters, and what makes people click your result instead of the next one.
4 min readUses the Meta Tag Generator
JPG, PNG, WebP or AVIF: Which Image Format Should You Use?
A plain guide to picking an image format for the web: what each one is good at, what it costs in file size, and a simple rule that covers almost every image.
4 min readUses the Responsive Image srcset Generator
How to Combine Images Into One PDF (and Keep It Small)
Turn photos or scans into a single PDF that prints at the right size, keeps pages in order and is small enough to email. Plus how to merge and split PDFs.
3 min readUses the Image to PDF Converter
Hashing vs Encryption vs Encoding: What Is the Difference?
Three ideas that get mixed up constantly. What each one does, which can be reversed, why Base64 is not security, and how passwords should really be stored.
3 min readUses the Hash Generator
How to Test a Webhook (and Why It Fails in Production)
See exactly what a webhook sends, test your endpoint before going live, verify signatures, and handle the retries and duplicates that break real integrations.
3 min readUses the Webhook Tester
HTTP Status Codes That Actually Matter, and When to Use Each
The dozen status codes you will really meet: 301 vs 302, 401 vs 403, 404 vs 410, 429 and the 5xx family, with what each means for users and for SEO.
4 min readUses the HTTP Status Code Reference
Regex Basics: Read and Write Regular Expressions Without Fear
The handful of regex pieces that cover most real tasks: character classes, quantifiers, anchors, groups and flags, with worked examples and the common traps.
3 min readUses the Regex Tester
Core Web Vitals Explained: LCP, INP and CLS in Plain English
What Google's three page experience metrics measure, the scores to aim for, and the fixes that move each one, from image sizes to layout shifts.
3 min readUses the Page Weight and Load Budget Calculator
SPF, DKIM and DMARC Explained: Why Your Emails Go to Spam
The three DNS records that prove your email is really from you, what each one checks, how they fit together, and how to set them up without breaking mail.
3 min readUses the Email Deliverability Checker
Robots.txt Explained: What It Blocks, and What It Cannot
How robots.txt really works, the rules search engines follow, why blocking a page does not remove it from Google, and a safe starting file for most sites.
3 min readUses the robots.txt Generator
Why Your Link Preview Shows the Wrong Image (and How to Fix It)
How Open Graph and Twitter card tags control the preview when a link is shared, the image size that works everywhere, and how to clear a stale cached preview.
3 min readUses the Open Graph Generator
Canonical Tags: Fixing Duplicate Content Without Losing Rankings
Why one page can live at many URLs, how rel=canonical tells search engines which one to rank, and the canonical mistakes that quietly cost traffic.
3 min readUses the Canonical and Pagination Tag Generator
Colour Contrast for Accessibility: WCAG Ratios Made Simple
What contrast ratios mean, the WCAG numbers to hit for text and buttons, why grey on white so often fails, and how to design for colour blindness.
3 min readUses the Contrast Checker
Flexbox vs Grid: Which One Should You Use?
The real difference between CSS Flexbox and Grid, a simple way to choose, and the common layouts each handles best, with code you can copy.
3 min readUses the Flexbox Playground
Cron Expressions Explained: Read Any Schedule in Seconds
What each of the five cron fields means, how to write every 15 minutes or weekdays at 9, the day-of-month trap, and why your job runs at the wrong hour.
3 min readUses the Cron Expression Builder and Parser
Unix Timestamps and Time Zones: Store Time Without Bugs
What a Unix timestamp is, seconds vs milliseconds, why you should store UTC and convert only for display, and the daylight saving bugs that catch everyone.
3 min readUses the Unix Timestamp and Date Debugger
Content Security Policy Explained: Add a CSP Without Breaking Your Site
What a Content Security Policy protects against, the directives that matter, why unsafe-inline undoes most of it, and a safe way to roll one out.
3 min readUses the Content Security Policy Generator
Cache-Control Headers Explained: Faster Repeat Visits, No Stale Pages
How browser and CDN caching works, what max-age, no-cache, no-store and immutable really mean, and the two-rule setup that suits most sites.
3 min readUses the Cache-Control Generator