Guides
A tool gives you an answer. These explain the thing behind the answer: why a file will not parse, why compression sometimes achieves nothing, what a privacy claim does and does not cover, and where a conversion quietly loses precision.
What “processed in your browser” really means
Which parts of a browser-based tool touch the network, which do not, and how to check for yourself in DevTools.
Fixing invalid JSON: the eight errors that cause most failures
Trailing commas, single quotes, unescaped characters, NaN, duplicate keys and large integers — with the exact parser message each one produces.
Password strength, measured properly
Why length beats complexity rules, how entropy is calculated, and what a generated password protects you from.
Hashing, HMAC and encryption are three different things
What each one is for, which of them you can reverse, and why MD5 still has a legitimate use.
Why PDF compression sometimes does nothing
What actually occupies space in a PDF, which files can shrink, and the trade-off you accept when pages are rasterised.
Choosing between PNG, JPEG and WebP
Transparency, artefacts, and why converting a PNG screenshot to JPEG usually looks worse at the same file size.
Writing regular expressions that do not hang
Greedy versus lazy quantifiers, the flags that matter, and the nested-repetition pattern that freezes a browser tab.
Reading and writing cron expressions
Field order, the difference between */5 and 5, the day-of-month and day-of-week trap, and how to sanity-check a schedule.
Where unit conversions lose precision
Binary versus decimal storage units, floating-point rounding, and how many digits you are entitled to keep.
How BMI, BMR and body-fat formulas are calculated
The equations behind the fitness calculators, the populations they were derived from, and where they are known to be wrong.