Arbitrum Gains 135% in September as Robinhood Chain Tops $1B

Arbitrum's ARB token climbed 135% over the month ending September 24, 2026, according to 247wallst, while Ethereum gained about 8% over September and Optimism's OP rose roughly 22% over a comparable window. The wider group of major Layer-2 tokens — including Arbitrum, Optimism, Starknet, zkSync and Mantle — reached a combined market cap of roughly $11.5 billion by September 22, a 65% recovery from its 2026 low, per CryptoRank data cited by CryptoTimes. By late September, CryptoTicker reported that Robinhood Chain held about $1.02 billion in its contracts, more than the total deposited on Polygon.

The single catalyst analysts kept pointing to was Robinhood Chain, a network launched by the brokerage on July 1, 2026 and built using Arbitrum's Orbit technology. Chainstack reported that a $1.92 million revenue day on Robinhood Chain on September 1 helped push ARB about 30% higher the same day. Yahoo Finance reported the chain had drawn roughly $146 million in tradeable tokenized stocks before Robinhood's free-gas promotion expired on September 29 — framing the end of that subsidy as the real test of whether the activity holds once users pay their own ETH fees.

Robinhood Chain settles its security back to Ethereum and charges transaction fees in ETH rather than ARB, and it has no native token of its own. L2Beat classifies it as an Arbitrum Orbit Layer 2 operated by Robinhood, focused on tokenized real-world assets such as stocks and ETFs plus on-chain services including lending, borrowing and 24/7 trading. Robinhood had already sold more than 200 tokenized U.S. stocks and ETFs to European customers in 2025, and the chain gives that business a dedicated settlement venue.

The link between the chain's growth and ARB's price runs through the Arbitrum Expansion Program, under which Orbit chains return 10% of net revenue to the ecosystem — 8% to the Arbitrum DAO treasury and 2% to a developer guild. On the September 1 revenue figure, that split would route about $192,000 in total, only $153,600 of it to the treasury. Arbitrum also activated the ArbOS 61 "Elara" release on August 20, 2026, adding compliance tooling for Orbit chains and expanding smart contract capacity.

The month was not uniformly positive. A lending protocol on Starknet lost $3.5 million to a manipulated price feed, and a smaller scaling network called Silicon began shutting down with close to $10 million stuck behind a withdrawal deadline. Starknet's STRK nonetheless rose 18% on September 18 to its highest level since June 19, 2026, while ARB gained about 17% that day and 26% over a trailing 24-hour window to roughly $0.2212. Ether closed September 18 at $2,611.34, up 6.8% on the day, per 247wallst.

Separately from token prices, L2Beat's Total Value Secured metric — tracking assets locked across Ethereum's scaling systems via canonical bridges and related contracts — reached $34.34 billion on September 30, 2026. That measure reflects a steadier accumulation of deposited value rather than a single month of trading.