space4.dev is a free collection of 70+ developer tools built for speed and privacy. It covers JSON formatting, validation, and conversion (to YAML, XML, CSV, TypeScript, Java, C#, and more), Base64/URL/HTML/Unicode encoding and decoding, JWT decoding and inspection, Unix timestamp conversion, cron expression parsing and generation, and OpenAPI/Swagger viewing, validation, and diffing.

Every tool runs 100% client-side in the browser — nothing you paste or upload is ever sent to a server. That makes it safe to use with sensitive data like auth tokens, API responses, or internal config files, which most competing tool sites don't guarantee.

No signup, no ads, and no account walls — each tool has its own dedicated, fast-loading page so you can jump straight to what you need instead of digging through a cluttered all-in-one dashboard.