Eight tools.
Zero fluff. All live.
No previews, no "coming soon" — every tool below is fully working right now, and every one of them runs entirely inside your browser on its own page. Check domains against the Kunch blacklist, generate and verify a public KID, validate a seed phrase, decode a raw transaction before you broadcast it. Nothing you type ever leaves your device.
Every tool on this site is plain client-side JavaScript — no accounts, no server calls, no telemetry, not even a web font from a CDN. To keep it forever: press Ctrl + S (Mac: Cmd + S), choose "Webpage, Complete", and open the saved file any time — with Wi-Fi off, in airplane mode, on a machine that never touches the internet.
Pick a tool.
Each one is its own page.
Every tool is self-contained: one URL, one job, zero setup. Bookmark the ones you use, save the ones you need offline.
01 Blacklist Checker
Check any domain against the Kunch JSON database of documented scam sites — offline.
Open the tool →02 KID Generator
A public, shareable KID from a Bitcoin key — all four major addresses, verified offline.
Open the tool →03 Seed Validator
Validate a BIP-39 mnemonic's words and checksum before you trust it.
Open the tool →04 Address Codec
Base58Check, Bech32 and EIP-55 addresses — identified, checksum-verified, explained.
Open the tool →05 Vanity Generator
Mine a Bitcoin address that starts with your chosen prefix — locally, never uploaded.
Open the tool →06 Hash Toolkit
SHA-256, Keccak-256, RIPEMD-160 and HASH160, computed locally as you type.
Open the tool →07 Tx Decoder
Read exactly what a raw signed Bitcoin transaction does — before you broadcast it.
Open the tool →08 Unit Converter
Wei, gwei, satoshi, msat — plus vB × sat/vB fee math. Exact BigInt arithmetic.
Open the tool →Download the page. Use it forever.
Every Kunch tool is a single HTML page with its JavaScript, fonts and data embedded — no CDNs, no build step, no server. Open any tool page, press Ctrl + S (Mac: Cmd + S), and choose "Webpage, Complete". The saved file opens in any browser, any time: with Wi-Fi off, in airplane mode, on an air-gapped machine that never touches the internet.
That is not a marketing claim — it is the design. The blacklist checker loads its scam-domain database from a JSON file that ships with the page; the KID generator runs its own SHA-256, RIPEMD-160 and secp256k1 implementations inline; the hash toolkit computes Keccak-256 and RIPEMD-160 in pure JavaScript. Nothing phones home, because there is no home to phone. The few tools that could optionally use network features (balance lookups, price feeds) deliberately don't, so an offline copy behaves exactly like the online page.
For sensitive work — generating a KID, validating a real seed phrase, decoding a transaction before broadcast — the offline copy is not just a convenience but the safer way to use the tool. Save it once, verify it works with the network off, and keep it on a USB stick.
Tools FAQ
Are the tools really offline? +
Yes. All eight tools are plain client-side JavaScript with zero network requests — no accounts, no server calls, no telemetry. Each tool lives on its own page; save that page with Ctrl+S / Cmd+S (Webpage, Complete) and it keeps working from the saved file, even with the network disconnected. The scam-domain database ships with the checker page as a JSON file.
Why does every tool have its own page? +
So each tool can be saved, bookmarked, shared and searched on its own terms — and so the saved copy is the smallest, most focused file for the job. If you only need the KID generator offline, you save one page, not eight.
Do I need an account or API key? +
No. Every tool is free and accountless, and the JavaScript runs in your browser. The separate Kunch API exists for teams that want the blacklist data programmatically, but the tools themselves never require it.
All eight tools.
Every one offline.
Blacklist Checker
Check any domain against the Kunch JSON database of documented scam sites — offline.
KID Generator
A public, shareable KID from a Bitcoin key — all four major addresses, verified offline.
Seed Validator
Validate a BIP-39 mnemonic's words and checksum before you trust it.
Address Codec
Base58Check, Bech32 and EIP-55 addresses — identified, checksum-verified, explained.
Vanity Generator
Mine a Bitcoin address that starts with your chosen prefix — locally, never uploaded.
Hash Toolkit
SHA-256, Keccak-256, RIPEMD-160 and HASH160, computed locally as you type.
Tx Decoder
Read exactly what a raw signed Bitcoin transaction does — before you broadcast it.
Unit Converter
Wei, gwei, satoshi, msat — plus vB × sat/vB fee math. Exact BigInt arithmetic.