Comparisons
Straight answers to the 'which should I use' questions — CSS units, redirect codes, layout systems, image formats and config languages, compared side by side.
301 vs 302 Redirect
One is permanent and aggressively cached, the other is temporary and reversible. Choosing wrongly is hard to undo.
401 vs 403
The names are backwards: 401 is about authentication, 403 is about authorisation. Retrying helps with one and never with the other.
Flexbox vs CSS Grid
Not rivals. Grid controls two dimensions at once, Flexbox controls one — and most real pages use both.
JSON vs YAML
JSON is unambiguous and machine-first. YAML is readable and human-first — and its convenience is exactly where its bugs come from.
PNG vs JPG vs WebP
One is lossless, one is lossy, one does both. Matching the format to the image type matters more than any compression setting.
px vs rem vs em
Three units, one real question: what is each one relative to? That single difference decides which to use where.