Longer write-ups on the formats and problems the tools here deal with — why JSON refuses to parse, what a structural diff does that a text diff cannot, the ways YAML quietly changes your values, what is really inside a JWT, and how text and image encoding go wrong. Written to be useful whether or not you use the tools.
Why a screenshot saved as JPG looks smeared, why a photograph saved as PNG is ten times too big, what WebP actually saves you, and the generation loss that makes re-encoding a bad habit.
Three encodings that solve three different problems, and the mojibake, padding errors, and double-encoded URLs that follow from confusing them. What each one is for, and how to recognise each failure.
A JWT is three Base64URL segments, and the payload is readable by anyone holding the token. Here is what each part contains, what the signature does and does not prove, and the alg:none attack that follows from getting it wrong.
YAML is readable until it is not. The Norway problem, version numbers that become floats, tabs that are illegal, and indentation that changes meaning — the failure modes worth knowing before they reach production.
A text diff compares characters; a structural diff compares data. For JSON, XML, and spreadsheets the difference decides whether you get five real changes or four hundred false ones. Here is how each works and when to use which.
JSON parse errors point at a position, not a cause. Here are the nine mistakes that produce nearly all of them, why the specification rejects each one, and how to find the real culprit when the reported position is misleading.