How IOST works: Proof of Believability, speed and smart contracts

The IOST tech in brief

Here is the short version. The IOST mainnet is a single chain that produces a block every 0.5 seconds. Block production rotates among 17 producers elected by token-holder votes, which the project calls Proof of Believability. Smart contracts are written in JavaScript and run on Google’s V8 engine. Users do not pay a fee per transaction; they pledge IOST to get gas that refills daily, and buy RAM for storage. The chain is fast and cheap to use, but it has never come close to the 100,000 transactions per second the whitepaper advertised, and the sharding design that was meant to get there was never deployed.

Since 2025 there is also a second network: the IOST Layer 2, an OP Stack rollup on BNB Chain. It uses a completely different stack, with EVM contracts and gas paid in BNB. This page focuses on the original chain, because that is where IOST’s own technology lives. For the new network and the BEP-20 token, read our IOST 3.0 and Layer 2 guide. For background on the project and its people, start with what IOST is.

Proof of Believability, on paper and in practice

The 2018 whitepaper describes Proof of Believability (PoB) as a “believable-first” approach. A small league of highly trusted nodes processes transactions optimistically, and a larger normal league checks a sample of their work. Trust comes from a believability score that mixes token balance, contributions, reviews and a special reputation token called Servi. Servi cannot be traded and destroys itself after use, so the idea was that nodes could not simply buy influence. The normal league was meant to run a Byzantine fault tolerant protocol based on ByzCoin and CoSi, with PBFT as a fallback.

The live mainnet is simpler. In practice PoB works much like delegated proof-of-stake. Token holders vote, one IOST for one vote, and you can split your votes across several nodes. A candidate needs more than 2.1 million votes and an audit to become a full node, and only producing nodes, which the docs call servi nodes, make blocks. The chain’s producer list holds 17 witnesses, while the explorer shows hundreds of registered candidates. The producer committee is re-elected every 10 minutes, and each producer makes six blocks in a row before passing the turn. If you remove your votes, the tokens stay locked for 72 hours. Our staking guide covers rewards and how to vote.

Why does this matter to an ordinary holder? Because it decides who you are trusting. With 17 producers, IOST is fast but relatively centralized, closer to EOS and TRON than to Ethereum or Cardano. The believability score adds some nuance, but the vote count is what gets a node into the committee. And since large exchange custody accounts hold much of the native supply, exchanges have real weight in that vote, which we discuss on the tokenomics page.

Block time and finality

A new IOST block arrives every half second, and researchers who measured the chain saw it keep that pace closely: 385 blocks in 192.5 seconds. So when you send IOST, your transaction usually lands in a block almost immediately. Landing in a block is not the same as being final, though. A block becomes irreversible once more than two thirds of the producers have confirmed it. In measurements, the last irreversible block trailed the newest block by about 62 blocks, which is roughly 31 seconds. The exchange integration docs round this up to about 40 seconds.

That gap explains a common question. Your wallet may show a transfer as sent right away, but an exchange will only credit it once the transaction is marked IRREVERSIBLE. On a normal day that is well under a minute. Delays beyond that usually come from the exchange itself, a missing memo or a maintenance pause, as happened when exchanges stopped IOST deposits for a few days around the v4.0.0 upgrade in October 2026. Our guide to sending IOST explains what to check, and the IOST explorer shows the status of any transaction hash.

JavaScript smart contracts

IOST’s most distinctive choice is the language. Smart contracts on the mainnet are written in JavaScript and run on an embedded V8 engine, the same engine that powers Chrome and Node.js. A contract’s interface is described in a JSON ABI file marked with the language “javascript”. For developers who already know web development, this lowers the barrier compared with learning Solidity, C++ or Haskell. The trade-off is a smaller toolset: the Ethereum world’s audit tools, libraries and developer communities do not carry over.

The tooling has evolved. The original iost.js SDK still exists, and in 2026 the team released ivem, a TypeScript SDK modeled on the popular viem library, plus ivem-kit for React and Vue front ends. The node software, go-iost, is open source under the LGPL-3.0 licence. Its v4.0.0 release in October 2026 was mandatory and not backward compatible, updating the stack to newer Go and Ubuntu versions. The explorer counts roughly fifteen hundred deployed contracts in total, which gives a sense of how small the developer ecosystem stayed. Our DApps and DeFi page covers what was actually built.

Gas and RAM instead of fees

IOST borrows the resource idea from EOS but adds its own twist. You do not spend IOST on each transaction. Instead you pledge IOST, and the chain gives you gas. Pledging 1 IOST gives 100,000 gas immediately and another 100,000 gas per day, up to a cap of 300,000 gas per pledged IOST. Gas cannot be transferred or sold, and the gas you use is destroyed. If you want your IOST back, unpledging takes 72 hours. The official docs describe this model as a middle path between Ethereum-style ownership and EOS-style rental.

Here is a worked example. Every new account starts with 10 IOST pledged, which produces 1,000,000 gas per day. A normal transfer uses about 9,000 gas, so that minimum pledge covers roughly 100 transfers a day at no cost. Failed transactions still use gas, so the allowance is not unlimited. Storage is the other resource. RAM is bought from the system on a pricing curve that rises as free RAM runs out, with a 2% fee on purchases that is burned. At recent prices, 1 KB of RAM cost roughly 1.6 IOST, and you can sell RAM back later. Sending IOST needs no RAM purchase at all.

Pledge, don’t pay

On the IOST mainnet, gas comes from pledged tokens that you can get back after 72 hours. RAM is the only resource you buy.

Accounts fit the same logic. IOST uses human-readable account names of 5 to 11 characters, using lowercase letters, digits and underscores, instead of long hex addresses. A new account must be created by an existing one, which locks about 10 IOST for gas and usually buys a little RAM, so the full setup comes to about 11.6 IOST. Accounts have separate owner and active keys, and support multi-signature permissions. For wallet choices that handle this for you, see our IOST wallets guide.

Real TPS vs the 100,000 claim

Throughput is where marketing and reality split the most. The 2018 whitepaper promised up to 100,000 TPS. Public testnets in 2018 reported 7,000 to 8,000. Later official copy talked about thousands of TPS, and a December 2024 post spoke of a consistent 10,000 plus. The best real-world number we have comes from the official IOSTSCAN explorer, which lists an all-time maximum of 3,388 TPS. That is a respectable peak for a single chain, but it is a long way below the headline.

Everyday load is far lower still. On a normal day the explorer shows about two transactions per second, and most of those are the automatic block-reward transaction included in every block. The chain was tested hard once: in December 2023, a wave of inscription spam congested it, and the developers shipped emergency releases that prioritized native transfers and temporarily hard-limited TPS to protect the system. So the honest summary is that IOST is fast enough for what it carries, but its capacity has never been proven anywhere near the original promise. For how this links to price and adoption, see our risk check.

Want to try a half-second chain yourself?

Buy IOST on a regulated exchange in your country if one lists it. Otherwise, start by buying crypto with a card, for example on CEX.IO, which has run since 2013, and move it to an exchange with an IOST market. CEX.IO does not list IOST and does not serve Japan.

Level up: open account

What happened to sharding

Sharding was the part of the design that was supposed to deliver the 100,000 TPS. The whitepaper describes Efficient Distributed Sharding (EDS), with a leader-election method called TransEpoch inspired by Algorand and OmniLedger, and a two-step protocol called Atomix for transactions that cross shards. Together, these would have split the network into parallel groups that each process part of the load.

None of this is visible on the live network. The node API exposes one chain with one set of producers, and there is no sign of multiple shards or cross-shard transactions. We found no announcement that sharding was switched on, and the IOST 3.0 plan moved the scaling story to a Layer 2 instead. In our view it is fair to say that sharding was designed but never shipped as described, and any article that lists sharding as a working IOST feature is repeating the whitepaper rather than describing the chain.

The Layer 2 side

IOST 3.0 added a second network with very different technology. The IOST Layer 2 is an optimistic rollup built on the OP Stack that settles to BNB Smart Chain, with chain ID 182 and gas paid in BNB. Its code is closely based on BNB Chain’s own opBNB. Contracts there are written in Solidity, like on any EVM chain, and withdrawals back to BNB Chain take seven days to finalize, as is normal for optimistic rollups. The docs claim more than 5,000 transfer TPS and gas fees around $0.001.

Those claims have not been tested by real demand. When our researchers sampled thousands of blocks across the network’s history, they found no user transactions, only the automatic system transaction each block carries, and the measured block time no longer matched the documented one. The official BEP-20 IOST token lives on BNB Chain itself, not on the Layer 2, and the L2 bridge moves only BNB so far. The full picture, with contract addresses and bridges, is on our IOST 3.0 page.

IOST vs Cardano, EOS, TRON and Ethereum

Comparisons only help if they compare like with like, so we keep this one to facts each project documents and avoid made-up speed rankings. IOST’s closest relatives are EOS and TRON: all three launched mainnets in 2018 or 2019 and use a small set of vote-elected block producers. Ethereum and Cardano sit at the other end, with proof-of-stake systems that spread block production across far more validators or stake pools, and both lean on Layer 2 networks for higher throughput.

The table shows a pattern. IOST’s real advantage over Ethereum and Cardano is speed and cost on the base layer: half-second blocks and gas from pledged tokens make small transfers cheap and quick. What it gives up is decentralization and ecosystem. Ethereum and Cardano have far larger validator sets, developer communities and DeFi activity, while IOST’s contract count stayed in the low thousands. Cardano also took a slower, research-first path, adding smart contracts only in September 2021, years after its 2017 mainnet.

IOST vs Cardano in one line

IOST bets on a few fast producers and JavaScript; Cardano bets on many stake pools and Haskell-based contracts. People searching for “IOST vs ADA” are really comparing those two philosophies.

Against EOS, the differences are more subtle, because IOST copied a lot from it: named accounts, block producers chosen by votes and a RAM market for storage. Here is how the two compare on the points both projects document.

TRON is the third sibling from that generation. It also uses elected producers, 27 Super Representatives, but it chose EVM-compatible Solidity contracts, which made it easy for Ethereum developers to move over. IOST’s JavaScript bet was arguably friendlier for web developers, but it left IOST outside the EVM world until the Layer 2 arrived. That is one reason the project moved to BNB Chain for its 3.0 phase.