Guides

Short, practical explanations of the problems these tools help with. Examples are checked against real runtimes.

• How to Debug API Responses: A Practical Workflow

  A step-by-step workflow for failing API calls: status codes, headers, HTML-instead-of-JSON errors, response diffs, JWTs, timestamps and URL encoding.

  Updated 2026-10-23

• How to Compare Two JSON Files

  Why text diffs mislead for JSON, how key order, array order, null and type changes should be treated, and how to compare JSON with jq, Node.js and Python.

  Updated 2026-10-28

• URL Encoding Explained with Practical Examples

  How percent-encoding works, encodeURIComponent vs encodeURI, + vs %20 and double encoding, with tested JavaScript, Python and curl examples.

  Updated 2026-10-23

• JWT Decoding vs. Signature Verification

  Why anyone can read a JWT, what decoding does and does not prove, and how servers should actually verify tokens.

  Updated 2026-10-23

• How to Format and Validate JSON (jq, Python, Node)

  Pretty-print, minify and sort JSON, see how formatters change numbers, and validate JSON with tested jq, Python and Node.js commands, in code and in CI.

  Updated 2026-10-28

• Common JSON Syntax Errors and How to Fix Them

  Trailing commas, single quotes, unquoted keys, raw line breaks and other mistakes that make JSON.parse fail, with fixes.

  Updated 2026-10-23

• How to Monitor an API Endpoint for Free

  What to check beyond uptime, tested curl, jq and Node.js check scripts, and the free tiers of UptimeRobot, Better Stack, Checkly and Uptime Kuma.

  Updated 2026-10-28

• Flutter JSON Errors: "is not a subtype" Explained

  Fix Dart JSON errors in Flutter: String or List<dynamic> is not a subtype of Map<String, dynamic>, int is not a subtype of double, Null and FormatException.

  Updated 2026-10-30

• Parse DateTime from JSON in Flutter and Dart

  Parse API dates in Dart: ISO strings with and without offsets, FormatException: Invalid date format, Unix seconds vs milliseconds, and toIso8601String.

  Updated 2026-10-28

• Convert Local Time to UTC Without DST Bugs

  Convert local date-times and zone names to UTC in JavaScript, Python and SQLite: offsets vs time zones, strings without offsets, DST gaps and overlaps.

  Updated 2026-10-28

• Unix Timestamps Explained: Seconds vs Milliseconds

  What epoch time is, how to tell seconds from milliseconds, and how to convert timestamps to UTC correctly in common languages.

  Updated 2026-10-23