Browser-based developer tools
JSON tooling that runs locally, by design
devsmiths is a focused set of developer utilities — JSON formatter, validator, tree viewer, repair, converter, diff, JSON-to-types, plus an everyday toolbelt for Base64, JWT, hashing, UUID, timestamp conversion, slugs, colour codes, and HTTP status lookups. Built around three principles.
Private by design. Every conversion runs entirely in your browser. Your JSON, tokens, and files never leave the page — we don’t even have a server to upload them to. Fast. Pages load in milliseconds, parsers stream, and CPU-heavy tools (JSON-to-types via quicktype, large-file repair) run in Web Workers so the UI never blocks. Documented, not just deployed. Every tool ships with a How-to-use section, edge cases, and a 5–8 question FAQ. A growing library of long-form guides covers the concepts underneath.
Available in English and 繁體中文. No signup, no rate limit, no telemetry that follows you across the web.
Tools
JSON
Convert
Web
Encode
Generate
Text
Why devsmiths
Your data stays on your device
All parsing, formatting, conversion, and code generation happens in your browser. The page has no upload endpoint. You can verify this in DevTools → Network: no request fires when you paste a payload.
Fast on small inputs, honest about large ones
Sub-megabyte JSON renders instantly. Multi-megabyte files use streaming parsers and Web Workers so the page stays responsive; the docs tell you the practical ceiling for each tool, not marketing claims.
Bilingual, not auto-translated
English and 繁體中文 are first-class — every tool page, every guide, every FAQ is authored in both languages. No machine translation layer; the zh-Hant copy reads like it was written in Chinese, because it was.
Documented edge cases
JSON parsing has dozens of fiddly real-world failure modes — BOMs, trailing commas, NaN, BigInt, deep nesting. Each tool documents which of these it handles, which it rejects, and the error message you’ll see. No silent corruption, no mojibake.
Latest guides
All guides →JWT pitfalls and best practices
Five common JWT footguns — alg=none, weak HMAC keys, missing exp, trusting kid blindly, mixing JWS and JWE — and how to avoid each one in 2026.
Working With Large JSON Files
Strategies for JSON files that don't fit comfortably in memory — streaming parsers, NDJSON, chunking, compression, and tooling that doesn't choke.
What Is JSON? A Practical Introduction
JSON is the most common data-interchange format on the web. This guide explains its value types, syntax, and the gotchas that trip people up.
Safely Parsing JSON in JavaScript
JSON.parse looks simple but has sharp edges — prototype pollution, BigInt, untrusted input. A practical checklist for parsing JSON in production JS.
Frequently asked questions
- Is anything I paste sent to a server?
- No. Every tool runs entirely in your browser. The site is hosted as static HTML behind a Cloudflare Worker that serves the page and does nothing with the inputs — there is no API endpoint that accepts your JSON. Open DevTools → Network and watch: when you paste a payload, no request fires.
- Why build another set of JSON tools?
- Most JSON tools sit at one of two extremes. The polished commercial ones upload your input to a server — fine for public data, not fine for production payloads with tokens or PII. The quick-and-dirty ones run locally but ship with a textarea and a button and call it done. devsmiths sits in between: local execution, with a real editor, real diagnostics, and real per-tool documentation.
- Do you use cookies or track me?
- No tracking cookies. The site uses cookieless Cloudflare Web Analytics for aggregate page-view counts (no IP storage, no cross-site identifier). Google Analytics and AdSense are loaded in production only, and only after explicit consent via the Google-certified CMP (Funding Choices). EEA/UK/CH visitors see the consent UI on first visit; everyone else can open it from the footer Privacy settings link. Full policy on the Privacy page.
- Who built this and how is it maintained?
- devsmiths is built and maintained by a single named operator — see the About page for who, why, and the engineering log. The site is updated continuously; the sitemap lastmod on every page reflects real edit times. Source is private; bug reports and feature requests go through the Contact page.
- Can I use this offline?
- Yes, after the first visit. The site registers a service worker that caches assets, so tools you've loaded once keep working even without a connection. Tools and guides you haven't visited yet need to be loaded online first.