Blog & Guides
In-depth explainers on developer tools, calculators, and online utilities. Learn the math and code behind 696+ free tools.
19 articles in developer
XML Sitemap Generator Online Free — Create & Download sitemap.xml
Generate a valid XML sitemap online for free. Enter your URLs, set priorities, and download sitemap.xml ready to submit to Google Search Console. No signup needed.
How to Find and Remove Duplicate Lines in Text
Duplicate lines in logs, CSV exports, and lists waste space and cause bugs. Learn how to find and remove them instantly with a free online tool.
What Is a Palindrome? Definition, Examples, and How to Check
A palindrome reads the same forwards and backwards. Learn the definition, famous examples, and how to check any word, phrase, or number online.
How to Add Page Numbers to a PDF Free Online (No Software)
Step-by-step guide to adding page numbers to any PDF document online, free. Choose position, set a custom starting number — done in seconds.
How to Convert PNG to JPG Online Free — Instant, No Signup
Learn when and why to convert PNG to JPG, how to do it free online, and what happens to transparency. Batch convert up to 20 files at once.
How to Delete Pages from a PDF Free Online (No Acrobat Needed)
Remove specific pages from any PDF in seconds — free, no software, no account. Enter page numbers or ranges like 1,3,5-7 and download instantly.
How to Convert PDF to PNG Online Free — Each Page as an Image
Export every page of a PDF as a high-quality PNG image online, free. No Acrobat needed — upload, convert, and download in seconds.
How to Compress PDF Without Losing Quality (Free, No Signup)
Learn the fastest ways to reduce PDF file size online for free — without sacrificing readability or image quality. Works on any device.
How to Merge PDF Files Online Free — Combine PDFs in Seconds
Step-by-step guide to combining multiple PDF files into one document online for free. No software to install, no signup required.
What Is Base64 Encoding? A Complete Guide
Learn how Base64 encoding works, why it exists, and when you should (and shouldn't) use it — with a step-by-step example.
What Is JSON? A Complete Beginner's Guide
JSON explained from the ground up — syntax rules, data types, nested structures, comparison with XML, and common pitfalls to avoid.
CSS Color Formats Explained: Hex, RGB, HSL — Which Should You Use?
A complete comparison of CSS color formats — how hex, RGB, HSL, and modern color functions work, and when to use each one.
What Is a Unix Timestamp? Everything Developers Need to Know
Unix timestamps explained — the epoch, UTC vs local time, milliseconds vs seconds, the Year 2038 problem, and working with timestamps in code.
JWT Tokens Explained: How JSON Web Tokens Work
A complete guide to JSON Web Tokens — the three-part structure, signing algorithms, security considerations, and when to use JWTs vs sessions.
Binary, Octal, Decimal, Hex: Number Systems Explained
Understand how binary, octal, decimal, and hexadecimal number systems work, why computers use them, and how to convert between bases.
Regular Expressions (Regex) for Beginners: A Practical Guide
Learn regex from scratch — syntax, character classes, quantifiers, anchors, and 10 practical patterns for validating emails, URLs, phone numbers, and more.
Markdown Syntax Guide: A Complete Reference
The complete Markdown syntax reference — headings, bold, italic, code, tables, links, images, lists, and GitHub Flavored Markdown extensions.
YAML vs JSON: When to Use Each and Key Differences
A complete comparison of YAML and JSON — syntax differences, YAML gotchas (the Norway problem!), and when each format is the right choice.
CSS Specificity Explained: Why Your Styles Aren't Applying
Master CSS specificity — how the cascade works, the specificity scoring system, the !important rule, and practical strategies to avoid specificity wars.