Free Developer & Data Tools
Format and validate JSON, convert between JSON and CSV, decode JWTs, hash files, generate UUIDs and QR codes, diff text, and unzip or create ZIP archives — all directly in your browser tab. Nothing you paste or drop is ever sent anywhere.
That matters more for this category than any other on the site: developer tools routinely handle things that shouldn't leave your machine — a production API token pasted into a JWT decoder, a customer record pasted into a JSON formatter, a password hash you're debugging. Sending any of that to an unknown server, even "just to format it," is a real security anti-pattern many online tools quietly ask you to accept. Every tool here processes text and files locally; pasting a real token or a real payload to check its shape is exactly what these tools are for, and doing it here doesn't create a copy of it anywhere outside your tab.
How client-side data tools differ from server-based ones
Most in-browser and online JSON formatters parse through JavaScript's native JSON.parse, which silently coerces large integers — a 64-bit database ID, a Snowflake ID, a big serial key — into floating-point numbers, corrupting them the moment you format and re-save. Moyang's JSON formatter uses the lossless-json library instead, preserving big numbers exactly as written, so formatting a payload with a 19-digit ID doesn't quietly change its value.
The JWT decoder shows the header and payload exactly as they are, without attempting signature verification against any server — there's no server to check against, and no secret is ever transmitted. It's deliberately a "read what's inside" tool, not an auth-testing tool. Hash Generator computes MD5, SHA-1 and SHA-256 over either pasted text or a dropped file entirely through the browser's WebCrypto API (for the SHA family) plus a local MD5 implementation — useful for verifying a download's checksum without uploading the file anywhere just to check it.
Unzip parses only a ZIP archive's central directory to show a file listing instantly, decompressing only the specific file you choose to open, with limits against "zip bomb" archives — files whose declared size or compression ratio would blow past a safe memory budget — so a malicious download can't crash the tab.
Being upfront about the trade-offs: nothing is saved or synced anywhere — refresh the tab and your input is gone unless you've downloaded a result, which is a deliberate consequence of the privacy guarantee, not an oversight. There's no batch or API mode for these tools (paste one, hash one) — they're built for interactive checking, not pipeline automation. Text Diff and Case Converter operate on correct Unicode grapheme boundaries for most scripts, but very large pastes (several megabytes) can feel sluggish, since everything runs on your device's CPU rather than a server cluster.
In practice, that covers the common developer chores: checking what's actually inside a JWT before debugging an auth issue, reformatting a minified API response to read it, converting a CSV export into JSON for a script, generating a UUID for a new database record, verifying a downloaded file's SHA-256 against a published checksum, or opening a ZIP archive from an email attachment without installing anything.
FAQ
- Is it safe to paste real API tokens or production data into these tools?
- Yes. Nothing is sent anywhere — every tool here processes what you paste or drop entirely in your browser tab, and it's never transmitted or stored.
- Does the JWT decoder verify the signature?
- No — it only decodes and displays the header and payload. Verifying a signature needs the secret or public key, which isn't something a paste-and-view tool should be asking you for.
- Why does the JSON formatter handle big numbers differently from other tools?
- It uses the lossless-json library instead of JavaScript's native JSON.parse, which prevents large integers — like 64-bit database IDs — from silently losing precision when reformatted.
- Can I open a password-protected ZIP file?
- Not yet — encrypted entries are detected and shown, but can't be extracted.
- Is anything I paste or upload saved anywhere?
- No. Refreshing the page clears everything; nothing persists unless you explicitly download a result.