Why I Built 5 Developer Tools That Never Talk to a Server

Format stack — Wed, 19 Aug 2026 04:47:29 +0000

Every JSON formatter, regex tester, and Base64 tool I could find online works the same way: you paste your data in, it gets sent to a server, and you get a result back. For a throwaway public snippet, that's fine. For an API response with real customer data, an internal config file, or a token you're debugging at 2am — you've just handed that to a server you know nothing about.

That bugged me enough to spend time building the alternative: FormatStack, five utility tools that run entirely in your browser tab. Nothing you paste in is ever transmitted anywhere.

What's in it
JSON Formatter — pretty-print, minify, validate with real parse errors
Regex Tester — live match highlighting, capture groups, common presets (email, URL, phone, IP)
UUID v4 Generator — single or batch, via crypto.randomUUID()
Base64 Encoder/Decoder — proper UTF-8 handling (plain btoa() breaks on emoji and accented text — more on that below)
Cron Parser — plain-English translation plus next 5 run times, computed locally.

FormatStack is live at formatstack.tech.

DEV Community: Format stack

Why I Built 5 Developer Tools That Never Talk to a Server