Balancer
Balancer is a decentralized exchange and automated market maker on Ethereum and other EVM chains. Its distinctive feature is flexible pools: instead of the usual 50/50 two-token pair, a Balancer pool can hold up to eight tokens in custom weights, which lets a pool act as both a trading venue and a self-rebalancing index portfolio. Anyone can swap through these pools from their own wallet, and liquidity providers earn fees. Balancer launched in March 2020, built by Balancer Labs (founders Fernando Martinelli and Mike McDonald), is non-custodial, and is governed by holders of the BAL token.
What Balancer is
Balancer is a decentralized exchange and automated market maker on Ethereum and other EVM chains. Where a typical AMM pool holds two tokens in a fixed 50/50 split, a Balancer pool can hold up to eight tokens in custom weights — say 80/20 or an even spread across several assets. That flexibility means a single pool can serve two purposes at once: it is a place to trade, and it behaves like a self-rebalancing index fund, because arbitrage keeps the pool's holdings near their target weights. Trades settle on-chain from your own wallet, liquidity providers earn the fees, and the protocol is governed by holders of the BAL token. Balancer launched in March 2020, built by Balancer Labs.
How Balancer's pools work
A Balancer pool is defined by the tokens it holds and their weights, and its pricing formula generalizes the constant-product math so those weights stay balanced as people trade. This unlocks pool types beyond simple swaps: weighted pools that act like index portfolios, stable pools tuned for assets that track the same price, and “boosted” pools that route idle liquidity into lending markets for extra yield. Because pool creation is open, the tokens available range from blue-chips to brand-new, unvetted ones. Balancer also acts as liquidity infrastructure that other DeFi apps and aggregators build on, rather than only a consumer trading site.
Is Balancer safe?
Balancer's flexibility has come with real security incidents, and its record is more mixed than a plain two-token AMM. The most serious was in November 2025: attackers exploited a rounding/precision error in Balancer v2 Composable Stable Pools, draining roughly $128M across several chains in under half an hour. Only a fraction was recovered — Balancer secured about $19M via a counter-exploit and moved to redistribute a portion (around $8M) to affected liquidity providers, so most of the loss was not made whole. Treat the recovery as partial.
Earlier, in August 2023, Balancer disclosed a critical vulnerability in some v2 “boosted” pools and urged users to withdraw; despite mitigation, attackers still exploited unwithdrawn funds for nearly $900K via flash loans. Beyond specific bugs, the usual DeFi risks apply — smart-contract risk (heightened by Balancer's complex pool math), scam tokens from permissionless pools, and phishing sites or malicious approval prompts. Confirm the official domain and review what you sign.
Incident record
Attackers exploited an arithmetic precision-loss (rounding) flaw in Balancer v2 Composable Stable Pools, using crafted batchSwap operations to drain roughly $128M across six chains in under 30 minutes. Balancer recovered about $19M through a white-hat counter-exploit and moved to redistribute around $8M in kind to affected liquidity providers; the large majority of the loss was not recovered.
Days after Balancer disclosed a critical vulnerability in some v2 boosted pools and urged users to withdraw, attackers still exploited funds that had not been withdrawn, taking nearly $900K via multiple flash-loan attacks. Most at-risk liquidity had been secured before the exploit, but the drained funds were not recovered.
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Frequently asked
Is Balancer safe?+
Balancer is non-custodial, but its record is mixed. In November 2025 attackers drained about $128M from v2 Composable Stable Pools via a rounding-error exploit, and only a fraction (~$19M) was recovered. In August 2023 a boosted-pool bug led to a ~$900K flash-loan exploit. Its complex pool math raises smart-contract risk, and standard DeFi risks — scam tokens, phishing, malicious approvals — also apply.
Was Balancer hacked?+
Yes, more than once. The largest was November 2025, when attackers exploited a precision/rounding flaw in Balancer v2 Composable Stable Pools and drained roughly $128M across several chains in under 30 minutes; about $19M was recovered and only part of that redistributed, so most was not made whole. A smaller ~$900K exploit hit boosted pools in August 2023.
What makes Balancer different from other DEXs?+
Balancer pools can hold up to eight tokens in custom weights, not just a 50/50 pair. That lets one pool be both a trading venue and a self-rebalancing index portfolio, and supports specialized pool types like stable pools and yield-boosted pools. The trade-off is more complex pool math, which has been a factor in its security incidents.
What changed
- 2026-09-28Profile created: what Balancer is as a multi-token weighted AMM, how its pools work, and the safety picture — the November 2025 v2 exploit (~$128M, partial recovery) and the August 2023 boosted-pool exploit (~$900K), plus DeFi-inherent and phishing risks.