Developer utilities,
in one native window.

Seven tools today

• Markdown

  A split editor and live preview with synchronized scrolling. The editor tints syntax as you type, and the preview follows the system appearance.

• JSON

  Format, minify, sort keys and validate. Your input is never rewritten — the result appears in a separate read-only pane, so a bad transform cannot lose it.

• CSV

  A spreadsheet-style grid with a tolerant parser, automatic delimiter detection, numeric sorting, multi-column sort, per-column filters and search.

• Mermaid

  A diagram editor with a live preview, rendered entirely offline. A broken edit never blanks the diagram — the last good render stays while you fix the line.

• Timestamp

  Paste a Unix time, in any unit from seconds to nanoseconds, or a date. See it in every common format, as local time and relative to now, and in the time zones you add.

• Encode / Decode

  Base64, URL, HTML and hex, in both directions. Decoding unpacks gzip and zlib, formats JSON, and shows anything that is not text as a hex dump.

• JWT

  Decode a token's header and payload, see whether it has expired, and check its signature against a secret or public key you paste. Nothing you paste is saved.

Your files stay on your Mac

VeloUtils is sandboxed. It reads and writes only the files you choose, through the system open and save panels or by drag and drop. It never modifies a file you opened. There is no account, no sign-in, no analytics and no telemetry.

The one qualification: the Markdown preview is a real web view, so it fetches a remote image if your document references one, exactly as a browser would. The privacy policy sets out the detail.

Requirements

macOS	26.0 (Tahoe) or later
Architecture	Apple silicon and Intel — a universal binary
Price	Free
Licence	MIT for the app's own code. The bundled Mermaid library folds in 76 open-source packages; their notices are in the app under Help › Acknowledgements.

File types

VeloUtils registers with macOS as an alternate handler for Markdown, JSON, CSV and TSV files, and as the owner of .mmd and .mermaid. Finder's Open With, a drop on the Dock icon, and open -a VeloUtils all open the file in the matching tool.