Offline Developer Tools That Work Without an Internet Connection

Most developer utilities on the web stop being useful the moment the connection does — and several of them were never safe to paste a token into in the first place. Toolbit is a complete toolbox that installs once and then works with the network unplugged.

Why offline matters more than it sounds

Offline is not only about aeroplanes. It is about the locked-down corporate network that blocks unknown domains, the air-gapped environment where regulated data lives, the customer site with hostile WiFi, and the simple fact that a tool which never makes a request cannot leak anything. When the formatter runs in your tab, "did that JSON contain a customer record?" stops being a question you need to answer.

How Toolbit works without a connection

Toolbit is a progressive web app. The first visit caches the application shell and every tool; after that the service worker serves them from disk. There is no API to call because every transformation — parsing, formatting, hashing, encoding — is implemented with standard browser APIs. Install the PWA to launch Toolbit from your device.

What is in the offline toolbox

Formatters for JSON, YAML, XML, SQL, CSS, and GraphQL. Encoders and decoders for Base64, URLs, HTML entities, JWTs, X.509 certificates, and protobuf wire format. Generators for UUIDs, hashes, passwords, TOTP codes, QR codes, and realistic test data. Converters for timestamps, colours, units, images, and CSV. Inspectors for regular expressions, diffs, git patches, and cron expressions. Plus an HTTP client and a WebSocket tester for the moments the network is back.

Installing for offline use

In a Chromium or Edge browser, use the install icon in the address bar. On iOS, use Share then Add to Home Screen. Cached local tools can then work without a connection. Network tools and analytics require a connection.

Start with these tools

• JSON Formatter Format, validate and beautify JSON instantly. Pretty-print, minify, sort keys, and pinpoint parse errors. Runs…
• JWT Decoder Decode a JWT and inspect its header, payload, and expiry. Tokens are decoded in your browser and never uploaded to a…
• Base64 Encoder & Decoder Encode text to Base64 and decode Base64 back to text, with URL-safe and UTF-8 support. Runs locally inside your…
• Regex Tester Test regular expressions with live match highlighting, capture groups, and replace preview. Runs locally in your…
• Hash Generator Generate MD5, SHA-1, SHA-256, and SHA-512 hashes from text or files. Computed in your browser — nothing is uploaded.
• UUID Generator Generate cryptographically random v4 UUIDs one at a time or in bulk, with formatting options. Runs locally in your…

Frequently asked questions

Do offline tools still get updates?

Yes. When you are next online the service worker fetches the new version in the background and applies it on the following load.

Is an offline web app as private as a native one?

In this case yes — local transformations do not upload input. Network tools send requested traffic, and optional analytics sends minimized usage events.

Which tools need a connection?

Only the API request builder and the WebSocket tester, which by definition talk to a remote endpoint. Everything else is pure computation.