Sigma9
Sigma9 Browser Extension
Sigma9 is a self-custody wallet for your browser. You hold USDC or USDT — and the network fee is paid in the same asset you hold. You never need to keep a separate gas token (like ETH, MATIC, or SOL) just to move your money.
Gasless by design
Every supported send and bridge is gasless. The fee is quoted and paid in the asset you're moving — USDC for USDC, USDT for USDT. No native gas token, no top-ups, no "insufficient gas" dead ends.
Send, receive, bridge
Send USDC or USDT to any address, receive to your own, and bridge where a real route exists — from one screen. Cross-chain USDC uses Circle CCTP v2 — canonical burn on the source chain, mint on the destination. No wrapped tokens. For USDT, the only live USDT0 bridge route today is Arbitrum → MegaETH.
Gasless on every supported network
Send and receive USDC gaslessly on each of these networks:
- Ethereum
- Arbitrum
- Base
- Optimism
- Polygon
- Unichain
- Monad
- World Chain
- Solana
And you can bridge USDC gaslessly between any of them. Move USDC from any network above to any other — in any direction, EVM to EVM, EVM to Solana, Solana to EVM — without ever holding a native gas token. Cross-chain transfers use canonical Circle CCTP v2 burn-and-mint, so there are no wrapped tokens and no third-party bridge risk.
Gasless USDT (fee paid in USDT itself) is also live on Arbitrum, Polygon, Ethereum, MegaETH and Solana. Not on Unichain or Optimism; Base has no USDT. USDT cross-chain is partial — only Arbitrum → MegaETH is live today.
A dedicated Networks screen lets you enable or disable individual chains so the wallet shows only what you use.
Support matrix
| Network | USDC same-chain | USDC bridge | USDT same-chain | USDT bridge |
|---|---|---|---|---|
| Ethereum | Yes | CCTP v2 | Yes | — |
| Arbitrum | Yes | CCTP v2 | Yes | to MegaETH |
| Base | Yes | CCTP v2 | — (no USDT) | — |
| Optimism | Yes | CCTP v2 | — | — |
| Polygon | Yes | CCTP v2 | Yes | — |
| Unichain | Yes | CCTP v2 | — | — |
| Monad | Yes | CCTP v2 | — | — |
| World Chain | Yes | CCTP v2 | — | — |
| Solana | Yes | CCTP v2 | Yes | — |
| MegaETH | — (no USDC) | — | Yes | receive only (from Arbitrum) |
Same-chain sending is the baseline for every network above — cross-chain bridging is partial and per-token. MegaETH is USDT-only (no USDC) and bridge-destination-only: it can receive USDT0 from Arbitrum but has no route out yet.
Your keys stay yours
True self-custody. The wallet stores your seed encrypted, locally, in the browser. The decrypted seed is never persisted — it is decrypted only in memory to sign a single transaction and wiped immediately afterward. There is no server that holds your keys.
No dApp connections. No blind signing.
Sigma9 does not inject a wallet provider into web pages and does not connect to dApps. It never asks you to sign an opaque smart-contract call or grant a token approval. The wallet does exactly three things — send, receive and bridge the assets it supports — and nothing on a web page can ask it to move your funds. The entire "connect wallet, approve a malicious contract, watch it get drained" attack surface simply isn't present.
Security hardening
A double-spend guard verifies on-chain state before ever resending a transaction. Address inputs are protected against address-poisoning and clipboard-clipper attacks. Crypto-critical dependencies are exact-pinned. No analytics, no telemetry, no tracking.
The browser extension is its own build and may differ from the mobile app — each platform ships independently.
Have questions? See the Sigma9 FAQ →.
Sigma9 — gasless self-custody. Network fees paid in the asset you hold (USDC or USDT). Keys stay on your device.