Developer guides
Practical articles about the problems behind the tools: why a JSON document fails to parse, what a server must check before trusting a JWT, which regex patterns can freeze a server, what a 502 actually means, and how to ship a container to Kubernetes without surprises. Each guide has tested code examples and links to a tool you can use to try the ideas straight away.
There are 26 guides, at least one for every tool category. New guides are added over time; each one shows when it was published or last updated.
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JSON syntax errors: the 10 most common and how to fix themTrailing commas, single quotes, comments, NaN, BOMs and HTML error pages: how to recognise each JSON.parse failure from its message and fix it.How JWTs work: header, payload, signature, and why decoding is not verifyingWhat is inside a JWT, how HS256 and RS256 signatures work, and the exact checks a server must run before trusting a token.Base64 explained: what it is, what it is not, and the URL-safe variantHow Base64 turns bytes into text, why it is not encryption, why output grows by a third, and how Base64URL differs.Unix timestamps: seconds vs milliseconds, the 2038 problem and time zonesStore instants as UTC timestamps, tell seconds from milliseconds, understand the 2038 overflow, and avoid time zone and DST bugs.Regex cheat sheet with real examples, and how to avoid catastrophic backtrackingCharacter classes, quantifiers, anchors, groups, lookarounds and flags with tested examples, plus why some patterns freeze a server and how to fix them.HTTP status codes you will actually run into, and what to do about themThe status codes behind most failed requests, from 301 and 401 to 413, 429, 502 and 504: what usually causes each one and how to fix or handle it.YAML pitfalls: indentation, the Norway problem and anchorsThe YAML behaviours that break real configs, from unquoted "no" becoming false to tabs, anchors, merge keys and multi-line strings.Writing a production-ready Dockerfile: multi-stage builds, layer caching and non-root usersTurn a naive Dockerfile into a small, fast-building, non-root image step by step, with .dockerignore, cache mounts, signals and health checks.Kubernetes Deployment, Service and Ingress: a minimal working exampleDeploy a web app to Kubernetes with three short manifests, understand how labels, ports and selectors connect them, and debug the usual failures.MD5 vs SHA-256 vs bcrypt: which hash to use for whatChecksums, HMAC signatures and password storage need different hash functions. What each guarantees, and code for doing each job correctly.