Guides for everyday data problems
Fifteen short, answer-first guides to the data problems these tools exist for, each one links straight to the tool that does the job, locally in your browser.
- Pretty-print JSON with jq, Python and JavaScript
Copy commands for jq, python -m json.tool and JSON.stringify. Learn how each handles JSON Lines, invalid input and large integers.
- How to fix “Unexpected token” in JSON
Unexpected token means the parser hit illegal syntax: a trailing comma, single quotes, comments or an HTML error page. Find the exact line locally.
- JSON vs YAML vs CSV: which format for which job?
JSON for APIs and precision, YAML for human-edited configs, CSV for tabular exports, how data model, comments and types decide, with converters.
Tool: JSON ↔ YAML Converter
- How to decode a JWT (and why that isn't verifying it)
Split the token on its two dots and Base64URL-decode the first two segments, no key needed. Decoding shows the claims but never verifies anything.
Tool: JWT Decoder
- Base64 vs Base64URL
Base64 vs Base64URL differs by two characters (+/ vs -_) and = padding. Why JWT segments fail atob(), and how to convert locally in your browser.
- UUID v4 vs v7: random or time-ordered?
v4 is 122 random bits; v7 leads with a 48-bit timestamp so IDs sort by creation time (RFC 9562). v7 suits database keys, v4 hides creation time.
- SHA-256 vs SHA-1 vs MD5: which hash should you use?
Use SHA-256 for anything that matters, SHA-1 and MD5 are collision-broken and fit only legacy checksums. What broken means and when it bites you.
- Unix timestamps: seconds vs milliseconds
Count the digits: 10 means seconds, 13 means milliseconds. Mixing them lands in January 1970 or the year 56637, two bug signatures explained.
- How to fix “XML parsing error: not well-formed”
Not well-formed means a syntax break: mismatched tags, a raw ampersand, two roots or a BOM. Find the first error's line and column locally.
- JSON vs YAML vs XML: differences and when to use each
JSON for APIs, YAML for human-edited config, XML for SOAP, SAML and schemas. How the data models differ and how to convert locally.
Tool: JSON ↔ XML Converter
- What is a JWT? Structure, claims and how to decode one safely
A JWT is three Base64URL segments: header, payload and signature. Anyone can read the claims. Decode locally; never treat decode as verification.
Tool: JWT Decoder
- How to format SQL queries: style rules that make SQL readable
One clause per line, one keyword case, stacked joins, and a dialect that matches the log. Format SQL locally so literals never leave the device.
- What is UUID v7?
UUID v7 is a 128-bit RFC 9562 identifier whose first 48 bits are a Unix millisecond timestamp, so IDs sort by creation time. Mint one locally.
- What is Base64 encoding?
Base64 turns every three bytes into four ASCII characters (RFC 4648). It is encoding, not encryption. Encode or decode in your browser; nothing is uploaded.
- What is a CSV file and how to open one safely
A CSV file is a plain-text table (RFC 4180). Open it in your browser so CRM and payroll rows are never uploaded. Delimiters, quotes and a UTF-8 BOM explained.
Tool: CSV Viewer