Guides
ToolsByUs Guides are plain-English explanations of the formats and files people bring to the site: JSON, CSV, YAML, TOML, UUIDs, JWTs, color spaces and image formats. Every guide is dated, reviewed, and linked to the in-browser tool that does the job — so the explanation ends with the work done, not with a sign-up wall.
- What Is JSONA plain-English introduction to JSON syntax, types and escaping, with real examples.
- JSON Syntax Cheat SheetEvery RFC 8259 syntax rule with copyable examples and the errors parsers throw.
- JSON EscapingMandatory and optional JSON string escapes, unicode sequences and surrogate pairs.
- UUID VersionsEvery UUID version's structure, ordering and collision profile, with pick guidance.
- How Does Base64 WorkThe Base64 mechanism from first principles: grouping, padding and alphabet variants.
- JWT StructureHeader, payload and signature segments of a JWT, decoded and explained honestly.
- CSV RFC 4180 RulesThe RFC 4180 CSV grammar in plain language, and where real files deviate.
- YAML BasicsIndentation, scalars, the Norway problem and multi-line strings for YAML newcomers.
- HEX vs RGB vs HSLHEX, RGB, HSL and CSS color() compared for readability, precision and conversion.
- PNG vs JPG vs WebP vs AVIFCompression, transparency and support trade-offs across PNG, JPG, WebP and AVIF.
- How PDF Files WorkThe PDF object graph, page tree and xref table, and what corruption means there.
- Cron Expression SyntaxEvery cron field, range and special character, plus the DOW/DOM interaction trap.
Frequently asked questions
Are the guides free to read?
Every guide is free, carries no sign-up wall, and loads as pre-rendered HTML — the text is fully readable with JavaScript disabled. Each guide links to the free browser tool that performs the task it explains.
Who writes and reviews the guides?
Guides are written against the primary specifications — RFC 8259 for JSON, RFC 4180 for CSV, RFC 9562 for UUIDs — and reviewed on the schedule published on the About page. Each guide's review date is published in its structured data and in the sitemap, and the changelog records what changed in each release.
Can I use a guide as a reference in documentation?
Yes. A guide that rests on a specification ends with a Sources list linking every RFC or standard it cites, so you can quote the primary source directly rather than the guide.