Browser-local developer tools

Small tools for the ten-second problems.

Format a JSON payload, decode a token, check when a cron job really fires, or diff two configs. Every tool on this site runs inside your browser tab. Nothing you paste is uploaded, and there is no account to create.

No upload — verify it yourself
10 tools
Works offline
No signup, no limits

Find a tool

Filtering happens in the page — no request is made while you type.

Showing all 10 tools.

JSON Formatter Format, minify and validate JSON while you type. /json-formatter · Format / Convert
JSON to Go Struct Turn a JSON response into Go structs with json tags. /json-to-go · Format / Convert
Base64 Encoder / Decoder Encode and decode Base64, including URL-safe variants. /base64 · Encode / Decode
URL Encoder / Decoder Percent-encode for path segments, whole URLs and form bodies. /url-encode · Encode / Decode
Timestamp Converter Convert Unix timestamps to readable dates in any time zone. /timestamp · Time
UUID Generator Generate UUID v4 and sortable v7 in bulk. /uuid · Text
JWT Decoder Decode a JWT, read the claims, and actually verify the signature. /jwt-decoder · Auth / Security
Cron Expression Parser Explain a cron expression and list its real next run times. /cron-parser · Time
Regex Tester Test a regular expression with live highlighting and capture groups. /regex-tester · Text
Diff Checker Compare two texts line by line, with exact character changes. /diff · Text

The claim

Your input never leaves this tab

This is not a slogan. In November 2025, two of the most popular online formatter sites were found to have exposed more than 5 GB of user submissions — including live AWS keys and Stripe secrets — because they processed input on their servers. Files uploaded to a honeypot key were used by someone else within 48 hours.

Here is how to check that DevCvt is not doing that:

Open your browser's developer tools, switch to the Network tab, then use any tool on this site. You will see no request carrying your input.
Or switch off your network connection entirely and keep using the tools. They still work, because the computation is all local.
Tool code lives in plain JavaScript files under /_astro/. Search them for fetch( — the only third-party script on the site is the advertising tag described in the privacy policy.