Plain-language explanations of how the things behind our tools work.
How a name becomes an IP address through resolvers, root, TLD and authoritative servers, the record types, TTL and caching, and DNS security basics.
How an IP address splits into network and host parts, how to find a network and broadcast address, divide a /24 into four /26s and size a subnet.
Title, description, canonical, hreflang, robots.txt, Open Graph and JSON-LD explained with real generated examples and the mistakes that cost rankings.
What SPF, DKIM and DMARC each check, what their DNS records look like, how alignment works and a safe order for rolling them out to stop spoofing.
What a hash function does, the avalanche effect shown with real SHA-256 output, which algorithms are still safe, HMAC, and how to store passwords properly.
How the TLS 1.3 handshake, key exchange and certificate chain make a connection private and authenticated, what the padlock does not prove and why certificates fail.
The three parts of a JWT with a real decoded example, the registered claims, how servers verify the signature, HS256 versus RS256 and the pitfalls to avoid.
UTC, offsets and time zones, daylight saving, Unix time and the 2038 problem, leap years, week numbers and day counts, with every example run in code.
The six JSON value types, why parsing fails, traps with big integers and key order, JSONPath queries and converting JSON to TypeScript, TSV and more.
How words and reading time are counted, Flesch readability, naming-case styles, line diffs, sorting, de-duplication and escaping for JSON, regex and SQL.
What encoding is (and is not), how Base64 turns three bytes into four characters, why it adds a third, and the mistakes to avoid.
Place value in binary, octal and hexadecimal, converting 202 between all of them step by step, hex colours, bit operations and two's complement.
Hex, RGB and HSL are one colour, how the WCAG contrast ratio is computed with real pass and fail examples, colour-blindness and building accessible palettes.
JPEG, PNG, GIF, WebP, AVIF, HEIC and SVG compared with measured file sizes, lossy versus lossless, aspect ratio and print maths, and which tool to use.
QR versions and sizes, the four error-correction levels, exact capacity limits, and how UPC and EAN check digits are computed, verified with the real libraries.
Pseudo-random versus secure randomness, modulo bias, why naive shuffles are biased, streaks, exact lottery, dice and Secret Santa odds and fair brackets.
What standard deviation measures, a worked step-by-step example, why samples divide by n − 1, the 68-95-99.7 rule, z-scores and how spread becomes uncertainty.
The compound interest formula with a worked $10,000 example, how compounding frequency matters, APR versus APY, the Rule of 72 and the effect of regular saving.
Avalanche versus snowball on one worked example with real totals, why minimum payments take so long, and when consolidating a debt actually helps.
Auto, personal, student, business, mortgage, HELOC, lease and reverse-mortgage loans compared, with Canadian compounding, points break-even and factor rates worked out.
The loan payment formula, why early payments are mostly interest, a worked $200,000 example month by month, and how extra payments shorten the loan and save interest.
Gross to net pay, marginal versus effective tax rates built slice by slice, self-employment tax, freelance rates, raises, commissions, budgets and unit prices.
Regular saving, employer match, fees and inflation, traditional versus Roth, the 25x rule and 4% withdrawal test, annuities, pensions and RMDs, all computed.
BMR, TDEE and calorie targets explained with one worked example: three BMR equations, activity factors, the 7,700 kcal rule, macros and energy out.
The 280-day rule from the last period, conception, IVF and ultrasound dating, ovulation and fertile days, hCG doubling and weight-gain guidelines, with dates computed.
What EXIF stores inside a photo, where it sits in a JPEG, how to turn GPS degrees into decimal coordinates, why it is a privacy risk and how to remove it.
How the first bytes of a file identify its real type, a table of common signatures verified against real files, why extensions can lie and where signatures matter.