Guides

Practical guides to the formats and workflows behind the tools: Base64, JWTs, cron, CIDR, colour contrast and more.

• Blurring and pixelation are not redactionPixelated text has been recovered and blurred faces unblurred. What actually removes information from an image — and what only looks like it does.2026-09-13
• SVG backgrounds in CSS: data URIs, patterns and the currentColor trapA tiling SVG pattern is smaller than a PNG, sharp at any resolution and needs no extra request. Here is how to embed one properly, and the two rules that catch everybody.2026-09-13
• Why CSS gradients go muddy in the middle — and what actually fixes itA gradient between two vivid colours often sags through grey in the middle. That is the interpolation space, not your palette — what in oklch fixes, and when it changes nothing.2026-08-25
• Why your string length is wrong: code units, code points and graphemesThe same emoji counts as 1, 2, 7 or 11 depending on what is counting — and each answer is right for something. Which to use when, and the characters that cause trouble.2026-08-24
• UUID v4: what the 122 random bits buy you, and what they cost122 random bits make collisions a non-issue, do not make a UUID a secret, and make it a poor primary key. The reasoning behind all three.2026-08-12
• Unix timestamps: seconds, milliseconds and the 2038 problemA Unix timestamp is a count of seconds since 1970 with no timezone attached. Most bugs come from the three things that sentence leaves out — units, signedness and leap seconds.2026-07-29
• px, rem, em and % — which CSS unit to use whererem scales with the reader's font size, px does not, and em compounds when you nest it. The differences are small until an accessibility audit, so here is the rule for each one.2026-07-08
• Hashing, encryption and encoding are three different thingsOne is reversible by design, one is reversible only with a key, and one is not reversible on purpose. Mixing them up is how secrets end up in plain sight.2026-06-17
• WCAG colour contrast, explained without the mathsWhat the 4.5:1 and 3:1 thresholds mean, which text they apply to, and the mistakes that fail an audit even when the palette looks fine.2026-05-30
• Cron expression cheat sheet, with the fields people get wrongFive fields, a handful of operators, and two traps that cause most misfires. A practical reference for reading and writing cron schedules.2026-04-22
• How to decode a JWT — and why decoding is not verifyingA JWT's header and payload are plain Base64url, readable by anyone. Signature verification is the part that matters. Here is the difference, with the common failure modes.2026-03-04
• What Base64 encoding actually is (and when not to use it)Base64 is not encryption and not compression — it is a way to move binary through text-only channels. Here is how it works, what it costs, and when to reach for it.2026-02-11
• CIDR notation explained — what /24 actually meansThe number after the slash counts network bits, and everything else about a subnet follows from it. How to read a prefix, count usable hosts, and dodge the off-by-one traps.2026-01-21