macOS
Bellows
Developer tools that never send your data anywhere — because they cannot.
Every online JSON formatter and JWT decoder asks you to paste your data into someone else's web page. Often enough that data is a production token, a customer record, or an API response you would not email to a stranger. Bellows does the same work on your Mac, in a window that has no way to reach the network.
It cannot reach the internet
Bellows ships without a network entitlement, so macOS refuses outbound connections at the kernel level. Not a promise in a privacy policy — a permission the app does not have, and one you can confirm yourself with a single codesign command.
41 tools, browsable
Formatters for JSON, XML, SQL and Markdown. Encoders for Base64, URLs, HTML entities, hex and Unicode. A JWT decoder, hashes, UUIDs, passwords. Converters for timestamps, time zones, number bases, colours, byte sizes, IP subnets, YAML and CSV. Regex tester, text diff, cron builder, QR codes.
Grouped by what they do
Every rival is a search box that assumes you already know the name of the tool you want. Bellows sorts tools into categories you can browse, so you can find one without knowing what it is called.
Copy, press, done
Copy a JWT anywhere in macOS and press your shortcut — the right tool is already open with your token in it. Or press ⌘P and type; the launcher opens on whatever you used last.
Answers, not raw values
The JWT decoder says a token expired two years ago instead of printing 1700000000. The byte converter distinguishes KB from KiB. The semver tool knows 1.0.0-2 sorts below 1.0.0-10.
Native and small
SwiftUI, no Electron, no web wrapper. It looks like a Mac app because it is one.
Pay once. Every update included.
No subscription and no account. Unlike a perpetual licence that stops receiving updates after a year, buying Bellows once means every future version is yours too.
Verify the privacy claim yourself
You do not have to take it on trust. Run this in Terminal and read the entitlements the app was signed with:
codesign -d --entitlements - /Applications/Bellows.appNeither com.apple.security.network.client nor com.apple.security.network.server is in the list. Without them, macOS will not let the app open a connection.
Requirements
macOS 14.0 (Sonoma) or later. No permissions beyond access to files you open yourself. The JWT tool decodes and inspects tokens; it does not verify signatures — see the terms for what that means in practice.
Guides
Longer answers to the questions these tools exist for — what a JWT's claims mean, why a Base64 string sometimes refuses to decode, and the cron trap that fires a job far more often than intended. Read the guides.