Guides
Practical, plain-English guides to the ideas behind our tools — passwords, image formats, JSON, color, encoding, hashing and more. No jargon, no fluff.
How to Create a Strong Password (and Actually Remember It)
A practical guide to creating strong, secure passwords: length, randomness, common mistakes, passphrases and password managers. Written for real people.
GuidePNG, JPG or WebP: Which Image Format Should You Use?
Understand the difference between PNG, JPG and WebP, when to use each, and how compression affects quality and file size. A clear guide for the web.
GuideWhat Is JSON? A Beginner-Friendly Guide
Learn what JSON is, why it is everywhere in modern software, its syntax rules, and common mistakes. A clear introduction for beginners and non-developers.
GuideStatic vs Dynamic QR Codes: What's the Difference?
Understand how QR codes work, the difference between static and dynamic QR codes, and which one you need for print, marketing or personal use.
GuideBase64 and URL Encoding Explained (in Plain English)
What Base64 and URL encoding are, why they exist, how they differ, and when you'll run into them. A jargon-free explanation with practical examples.
GuideHow to Write SEO-Friendly URL Slugs
What a URL slug is, why it matters for SEO and usability, and the rules for writing clean, effective slugs. Practical dos and don'ts with examples.
GuideHashing Explained: MD5, SHA-256 and When to Use Them
What a hash function is, how it differs from encryption, why MD5 is broken, and where SHA-256 fits. A clear guide to hashing for non-specialists.
GuideColor Models Explained: HEX, RGB and HSL
Understand how digital colors work: what HEX, RGB and HSL mean, how they relate, and which to use when designing. A clear, practical guide.
GuideHow to Compress a PDF Without Wrecking the Quality
Why PDFs get huge, how PDF compression actually works, and practical ways to shrink a PDF for email without ruining it — including when to keep text selectable.
GuideHow to Merge and Split PDFs (the Right Way)
A practical guide to combining and separating PDF files: when to merge, how to extract pages, keeping the right order, and doing it privately in your browser.
GuideUnix Timestamps and Time Zones, Explained Simply
What a Unix timestamp is, why computers count seconds since 1970, how time zones and UTC fit in, and the famous Year 2038 problem — in plain English.
GuideBinary, Decimal and Hexadecimal, Explained for Humans
Understand number bases without the maths headache: how binary and hexadecimal work, why computers use them, and where you'll meet them (colors, bytes, addresses).
GuideWhat Is a UUID, and Why Is It Everywhere?
A plain-English guide to UUIDs: what they are, why they're practically unique without a central authority, the different versions, and when to use one.
GuideWriting for the Web: Word Count, Reading Time and Why They Matter
How long should a blog post be, what reading time really tells you, and practical ways word count and readability shape whether people actually read your writing.
GuideRegular Expressions: A Gentle Introduction
Learn what regular expressions are and the handful of patterns that cover most real needs — matching digits, words, and repetition — with practical find-and-replace examples.
GuideLearn the "why", not just the "how"
Our tools do a job in one click, but knowing the concepts behind them helps you make better decisions — which image format to ship, what makes a password strong, or why a URL slug matters for SEO. These guides are written to be genuinely useful on their own, and each one links to the free Outilo tools that put the ideas into practice.