Master MetaMask Snaps: Complete Tutorial Guide.

Okay, look. Every other "MetaMask Snaps" guide jumps straight into "install this, code that" without telling you Snaps aren't for regular users yet. You can't just grab the normal MetaMask and expect magic. Snaps are in beta ish mode, and honestly, most folks waste hours because they skip Flask. That's the developer version. Without it? You're toast. I usually tell friends: get Flask first, or don't bother.

Why does this matter? Regular MetaMask blocks snaps unless you're on the directory page, and even then, it's limited. Flask lets you play wild. Sound familiar? You've probably tried something, got stuck, rage quit. Not today.

First Things: Grab MetaMask Flask

Download it from the official site - search "MetaMask Flask" and hit the Chrome extension link. Install like any extension. Pin it. Unlock with a new wallet or import one. Don't use your main funds here. Testnet ETH only, like Sepolia.

Now, check if it's Flask. Open console in a blank tab: await ethereum.request({method: 'web3_clientVersion'}). See "flask" in there? Good. No? Wrong version. Update.

In my experience, this trips up 80% of newbies. Gas fees? Minimal, like 0.00001 ETH for snap installs. But you're not paying much yet.

Enable Developer Mode Quick

1. Right click Flask icon → Manage Extension.
2. Hit Details → Inspect views: background.html.
3. Console pops. That's your debug spot later.

Done. Five seconds. What's next?

Using Snaps: The Easy Way First

Don't code yet. Try existing ones. Head to snaps.metamask.io. Directory's got 30+ snaps. Pick Wallet Guard - blocks shady txs.

• Click "Add to MetaMask".
• Popup: review permissions. Like "endowment:longRunning" for background stuff? Okay if trusted.
• Connect. Install. Boom, active in Settings → Snaps.

ShapeShift? Same deal. Adds multichain. I use it for quick Solana peeks without swapping wallets. Fees? Network gas only, ~0.0005 ETH.

Potential issue: "Snap not found". Refresh Flask. Or toggle Developer Mode off/on. Fixes 90%.

Okay, Now Build Your Own Damn Snap

Time to make one. Prerequisites: Node 20.11+, Yarn. VS Code. That's it.

Terminal. Run: npx @metamask/create snap my first snap. Name it whatever. Waits ~10-20 secs, installs deps. Might whine about scripts - yarn run allow scripts auto. Then yarn start.

Boom. Serves at localhost:8080 (snap) and :8000 (demo dapp). Open :8000 in Flask.

Connect and Test the Default

1. Hit "Connect". Permissions popup - approve.
2. "Send message". Custom dialog in Flask: "Hello World".
3. Edit snap/src/index.ts: change "Hello" to "Yo, custom snap!".
4. Refresh demo → Reconnect. See your text? Hot reload magic.

Super short first win. Feels good, right?

Thing is, snaps extend MetaMask. JSON RPC calls. Like wallet_invokeSnap to ping yours. Permissions in snap.manifest.json: tweak initialPermissions. Need homepage? Add "endowment:homepage". Restart yarn start.

Tweak Permissions Without Breaking Shit

Permission	What It Does	When to Use
endowment:longRunning	Runs background tasks	Notifications, simulations
endowment:transaction insights	Analyzes txs	Wallet Guard style
snap_getBip44Entropy	Derives keys	Custom wallets (careful!)
endowment:display	Custom UI screens	Forms, dialogs

Start minimal. I usually just grab "homepage" and "display". More later. Mismatch? Install fails. Check console: errors scream why.

Real Example: Text Transformer Snap

Watched a dev stream this. Built a snap that fancy fies text - bold serif, strikethrough, medieval vibes. Inside MetaMask. No external sites. Here's how, step for step. Copied the vibe.

First, edit snap.manifest.json:

• proposedName: "TextTransformer"
• version: "0.1.0"
• initialPermissions: ["endowment:homepage", "endowment:display"]
• icon: drop SVG in images/ (200x200, bytes works)

Now snap/src/index.ts. Ditch default. Add JSX support - latest V12 stuff.

import type { OnRpcRequestHandler } from '@metamask/snaps types';
import { panel, text, heading } from "@metamask/snaps ui/jsx";
import { updateSnapUI } from "@metamask/snaps jsx"; // Maps for transforms
const boldSerifMap = {'a':'𝐀','b':'𝐁' / etc - fill from Unicode /};
const doubleStruckMap = {'a':'𝕒' / you get it /}; function transformText(input: string, map: Record<string,string>): string { return input.split('').map(char => map[char] || char).join('');
} export const onRpcRequest: OnRpcRequestHandler = async ({ origin, request }) => { switch (request.method) { case 'hello': return snap.request({ method: 'snap_dialog', params: { type: 'Alert', content: panel([ heading('Text Transformer'), text('Paste text below') ]) } }); case 'transform': const { text: inputText, style } = request.params; let map = boldSerifMap; // switch on style const result = transformText(inputText, map); // Update UI await updateSnapUI(snap.updateBlock('result', text(result))); return result; default: throw new Error('Method not found'); }
};

Demo dapp: add form. wallet_invokeSnap({ snapId: 'local:http://localhost:8080', request: { method: 'transform', params: {text: 'hello', style: 'bold'} } }).

Test: yarn start → demo → input "test" → transform. Medieval text pops in MetaMask UI. Copy paste to Twitter. Took 30 mins total.

Issue? "UI not updating". Check JSX imports. V12 needs @metamask/snaps jsx. yarn add it.

Debugging: Where It All Goes Wrong

Console in background.html. Logs everything. Errors like "Permission denied"? Manifest mismatch. "Snap not installed"? Reconnect.

Hot reload fails sometimes. Kill yarn start, yarn start again. Gas for local? Zero - localhost.

In my experience, Chrome extensions page: reload Flask unpacked if packed. But don't pack yet.

Advanced: dApp Integration

Hook snaps into your site. Like Hedera snap tutorial.

1. Connect: ethereum.request({method: 'eth_requestAccounts'})
2. Install: await ethereum.request({ method: 'wallet_enable', params: { snaps: { [snapId]: {} } } })
3. Get address: await ethereum.request({ method: 'wallet_invokeSnap', params: { snapId, request: { method: 'getEvmAddress' } } })
4. Send HBAR or whatever: input amount → invoke transfer.

Balances? Call getBalance. Fees ~0.000005 HBAR equiv. Create account by sending to EVM addr first.

Why bother? Users stay in MetaMask. No exports. Secure.

Publish? Kinda

Local's fine for dev. For real: build site with install button. <a href="https://your site.com/snaps/your snap.zip">Install</a>. Host on IPFS or GitHub Pages.

Directory? Submit to snaps.metamask.io. Review process. Not instant.

Pro tip: shasum in manifest. Verify integrity. Users trust more.

Trouble Spots I Hit Every Time

No lists here. Just venting. Yarn versions mismatch - stick to LTS Node. Flask crashes on tab close? Restart browser. Permissions creep: audit json weekly. UI JSX breaks on old Flask - update to latest.

Multichain snaps? Add chainId perms. Gas sims eat ~0.001 ETH/testnet. Budget it.

Honestly, once you're in, it's addictive. Built a tx insights snap once - flags high fees pre sign. Saved me 50 bucks.

Custom Components Quickie

Want interactive forms? Export SnapComponent. Like:

export const InteractiveForm = () => ( <form id="transformer"> <input name="text" /> <button action="submit">Transform</button> </form>
);

Handle in onInput: if (event.type === 'form:submit') { / transform / }. Reinstall to see.

Snaps vs Regular Extensions

Snaps	Extensions
Inside MetaMask sandbox	Separate popup
RPC extend	Full browser access
Permissions granular	All or nothing
Hot reload dev	Reload unpacked

Snaps win for wallet stuff. Extensions for broad tools.

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