Technical guides
Each guide digs into a topic the tools solve in one click: where the result comes from, how to work it out by hand, and which mistakes show up in practice. Every example opens in the matching tool with the values already filled in, so you can check it yourself.
Subnetting from the Bits: How to Calculate a Subnet by HandWork out the network, broadcast, mask, and host range of any IPv4 subnet straight from the bits, with two step-by-step worked examples.VLSM Step by Step: A Worked ExampleA complete VLSM exercise on a /24 with six subnets of different sizes: block sizing, assignment order, and what to do when the address space runs out.Crontab: 20 Real-World Examples ExplainedTwenty cron expressions for real jobs, from every 5 minutes to month-end, plus the most common traps: the day-field OR rule, unescaped % signs, and daylight saving time.Unix Timestamps and Time Zones: Handling Dates Without BugsThe difference between an instant, local time, offset, and time zone, what daylight saving time does, what to store in your database, and the classic bugs in JavaScript, Python, and SQL.How to Create Strong Passwords: Entropy ExplainedWhat password entropy measures, how many bits you need in practice, why the formula fails for made-up passwords, and when a passphrase is the better choice.Base64 Explained: How It Works, Padding, and VariantsHow Base64 turns every 3 bytes into 4 characters, why = and == appear, what base64url changes, and the most common mistakes when using it from code.URL Encoding Explained: Percent-Encoding, %20, and +Which characters need encoding in each part of a URL per RFC 3986, why a space is sometimes %20 and sometimes +, and the classic bugs: concatenation, double encoding, and double decoding.UUID v4 vs. v7: Which to Use and Why It Matters for Your DatabaseHow UUID v4 and v7 are built, why v7 keeps database indexes compact, what each version reveals, and how they compare to ULIDs, Snowflake IDs, and auto-increment keys.MD5, SHA-256, and bcrypt: Which Hash Function to Use for WhatIntegrity, message authentication, and passwords need different tools: how MD5 and SHA-1 fell, why HMAC prevents length extension, and why passwords call for Argon2id or bcrypt.GB vs. GiB: Why a 1 TB Drive Shows 931 GBThe difference between decimal and binary prefixes, what each operating system shows, where space really goes, and how to convert Mbit/s to MB/s.