A crypto wallet does not hold coins. It holds keys, and whoever controls the keys controls the funds. That makes wallet development one of the most security-sensitive kinds of software there is: one mistake in key storage, signing or transaction display can cost users everything, with no bank to call.
SemBricks develops custom crypto wallets for mobile, desktop and the browser, and integrates wallets into existing products. We focus on secure key management, clear transaction signing and a user experience that does not ask users to understand gas or chain IDs.
Types of Wallets We Build
- Mobile wallets for iOS and Android, with keys protected by the device's secure hardware and biometrics.
- Desktop wallets for power users and teams that need more control, larger screens and integration with local tools.
- Browser extension wallets that connect to dapps, with careful isolation between the extension and the websites it talks to.
- Hardware wallet signing: support for hardware wallets, so keys never leave the device.
- Embedded and smart wallets: wallets built into your app, often based on account abstraction with social recovery and gasless transactions through paymasters.
Want users to transact without holding gas? See gasless transactions for every method, from paymaster sponsorship and EIP-7702 to relayers and permit signatures.
Custodial or Non-Custodial?
The first design decision is who holds the keys. In a non-custodial wallet, only the user does. You never touch user funds, but you have to make backup and recovery simple enough that users do not lock themselves out. In a custodial wallet, your company holds the keys on behalf of users. That is easier for users but makes you responsible for securing the funds, and in the EU, custody of crypto-assets for others is a regulated activity under MiCA. We build both, and we recommend getting legal advice early if you are considering custody.
Security by Design
- Key storage in the platform's secure enclave or keystore, never in plain storage, never in logs.
- Clear signing: showing users in plain language what a transaction or signature request will do, including token approvals and EIP-712 messages, so they do not sign blindly.
- Phishing protection: warnings for known malicious contracts and unlimited approvals.
- Recovery: seed phrases done properly, or smart-account recovery through guardians, depending on the audience.
- Minimal dependencies: every third-party library in a wallet is attack surface, so we keep the list short and pinned.
Multi-Chain Support
Most users hold assets on more than one network. We build wallets that support Ethereum and other EVM chains, including layer 2 networks, and Solana, with reliable RPC access and fallbacks, token and NFT balances, and transaction history from indexed data. Connecting to dapps is done through standards such as WalletConnect.
Frequently Asked Questions about Crypto Wallet Development
Should we build our own wallet or integrate an existing one?
If your users already have wallets such as MetaMask or Phantom, integrating those is usually the best start. A custom wallet makes sense when the wallet is the product, or when you want a smooth onboarding for users who have never used crypto, for example with an embedded smart wallet.
Which blockchains can the wallet support?
Ethereum and other EVM chains such as Base, Arbitrum and Polygon, and Solana. Additional chains can be added later if the architecture is designed for it from the start.
Can users log in without a seed phrase?
Yes, with smart accounts based on account abstraction. Recovery then works through guardians or other methods instead of a seed phrase, and a paymaster can sponsor gas so users do not need tokens to get started.
Do we need a licence for a crypto wallet?
For a non-custodial wallet, where only the user holds the keys, usually not. Holding crypto-assets on behalf of others is regulated in the EU under MiCA. We are not lawyers: get legal advice for your specific case early in the project.
Who owns the code?
Ownership of the source code is set out in the contract, and the code can be fully yours, including documentation and tests.
Can you sign an NDA?
Yes, we sign an NDA on request before discussing details.
See also our overview of blockchain and web3 development.
Plan Your Wallet
Tell us who your users are, which chains they need and whether the wallet is the product or part of it. We will help you choose the right type of wallet and design it securely.
Book a free call about your wallet
Browser Extension Crypto Wallet Development
Custom browser extension wallets for Chrome, Firefox and Edge: secure key storage, dApp connection standards, readable signing, simulation and store review.
Desktop Crypto Wallet Development: Windows, macOS, Linux
Custom desktop crypto wallets for Windows, macOS and Linux: multi-chain, multiple seed phrases, built-in trading, market data, custom RPCs and signed updates.
Hardware Wallet Signing Integration: Ledger, Trezor, QR
Hardware wallet signing for your app or wallet: Ledger and Trezor integration, QR-based air-gapped signers, clear signing, derivation paths and multisig.
Mobile Crypto Wallet App Development: iOS and Android
Custom mobile crypto wallets for iOS and Android: secure enclave key storage, biometrics, passkeys and smart accounts, WalletConnect and push notifications.