Guides
Short, first-principles references written to sit alongside the free Polyatic tools. Each one explains how something actually works — reading a CIDR prefix by hand, what the five cron fields really mean, how three bytes become four Base64 characters — with concrete worked examples and honest notes on where the idea breaks down. No sign-up, no tracking; open one, learn the thing, then jump to the matching tool when you need to do it for real.
NetworkingIP addressing & subnets
Development & encodingData formats, tokens & patterns
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JSON Explained
The six value types with a worked example object, the strictness rules (double quotes, no trailing commas, no comments), JSON vs JavaScript literals, pretty-print vs minify, and parse errors decoded.
Read guide → -
Number Bases Explained
What positional notation and a radix actually mean, why digital hardware forced binary, why programmers read bytes in hex (1 hex digit = 4 bits), the number 156 worked across all four bases, hex in
Read guide →#RRGGBBcolors and byte dumps, and two's-complement in plain terms. -
Base64 Encoding Explained
Why three bytes map to four characters, where the
Read guide →=padding comes from, the URL-safe variant, the ~33% size cost — and why Base64 is encoding, not encryption. -
URL Encoding Explained
Why URLs are ASCII-only, reserved vs unreserved characters, how
Read guide →%XXhex escapes are built, the%20-vs-+space,encodeURIComponentvsencodeURI, UTF-8 multi-byte encoding, and the double-encoding bugs that bite. -
QR Codes Explained
The three finder patterns and the quiet zone a scanner needs, the four encoding modes and why
Read guide →HELLObeats a URL on capacity, versions from 21×21 up, the L/M/Q/H error-correction levels, and how Reed–Solomon repairs a damaged or logo-covered code. -
JWT Structure Explained
The three dot-separated parts of a JSON Web Token, the registered claims (
Read guide →iss,exp,aud…) in a worked example, and thealg:nonefootgun. -
Regex Quick Reference
Character classes, anchors, greedy vs lazy quantifiers, groups and all four lookarounds — each shown with a worked example and an honest note on what it misses.
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Hashing Explained
What a one-way cryptographic digest is, the avalanche effect (with a worked one-character-change example), why hashing is not encryption or encoding, MD5/SHA-1 broken vs SHA-256 — and why passwords need a salted, slow KDF.
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UUIDs Explained
The 128 bits behind the 8-4-4-4-12 hex string, where the version and variant digits live (with a worked field dissection), v4 opaque vs v7 time-sortable, honest birthday-bound collision odds, and UUID vs auto-increment keys.
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Time & schedulingWhen jobs run
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Cron Expressions Explained
What the five cron fields mean, how
Read guide →*/15steps and ranges work, and the day-of-month vs day-of-week OR trap that quietly doubles a schedule — ten real schedules decoded. -
Unix Timestamps Explained
The 1970 epoch from first principles, why timestamps carry no timezone, the seconds-vs-milliseconds digit test, the Year 2038 32-bit overflow and its 64-bit fix — with a worked two-way conversion.
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Design, color & accessibilityHow screen color works
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Color Models Explained
RGB as additive light on 0–255 channels, HEX as those channels in base-16 (with the
Read guide →#RGBshorthand rule), HSL's intuitive hue/saturation/lightness, the alpha channel, and#3366ccconverted by hand across HEX → RGB → HSL. -
WCAG Contrast Explained
What the contrast ratio measures, how relative luminance comes from linearized sRGB channels weighted
Read guide →0.2126R/0.7152G/0.0722B, the 4.5:1 / 3:1 / 7:1 AA and AAA thresholds, what "large text" means, and#767676on white worked out by hand.