Cardano (ADA) Explained: Ouroboros, Fees, Staking and Risks

Cardano is a proof-of-stake blockchain with smart contracts, and ADA is its native token, used for fees, staking and on-chain governance votes. This page covers how the Ouroboros protocol produces blocks, how fees are calculated, the fixed 45 billion ADA supply cap, how staking works without locking your coins, and the incidents and regulatory questions worth knowing about. Crypto assets are volatile and nothing here is financial advice.

What is Cardano?

Cardano is a layer-1 blockchain created in 2015 by Charles Hoskinson, an Ethereum co-founder, and Jeremy Wood. Its main development company, Input Output Global (IOG), grew out of Input Output Hong Kong. The network went live in September 2017 and later added staking, native tokens and Plutus smart contracts. ADA pays fees, earns staking rewards and gives holders a vote in on-chain governance.

The founding details appear both on Kraken’s Cardano page and in the US Securities and Exchange Commission’s 2023 complaint against Binance, which describes Cardano as built on “its own proof-of-stake consensus protocol called Ouroboros”. Cardano was developed in eras with names such as Byron, Shelley, Alonzo and Voltaire; each era was introduced through a hard fork rather than a new chain.

Cardano uses an extended UTXO model, closer to Bitcoin’s accounting than Ethereum’s account balances. Each transaction spends specific outputs and creates new ones, which makes fees predictable before you sign but means smart contracts are written differently from Ethereum’s. Tokens on Cardano are native assets carried in outputs, not separate smart contracts.

How does Cardano’s Ouroboros proof of stake work?

Ouroboros splits time into one-second slots grouped into epochs of 432,000 slots, or five days. In each slot a stake pool may be elected as leader with a probability proportional to the ADA delegated to it, and on average one block is produced about every 20 seconds. Pools that win a slot produce the block; delegators share the rewards without running any software.

The figures come from Cardano’s node documentation, which says one node is expected to be nominated every 20 seconds on average, for about 21,600 nominations per epoch. Many slots are empty by design, which leaves time for blocks to propagate around the world before the next one appears.

How many blocks you wait for depends on the value at stake. Cardano’s documentation explains that a block is treated as final once it is deep enough in the chain, without a fixed number. Exchanges set their own confirmation requirements for ADA deposits, so crediting time varies by platform.

How much does a Cardano transaction cost?

Cardano fees follow a published formula: 44 lovelace for every byte of the transaction plus a fixed 155,381 lovelace. A simple ADA transfer usually costs about 0.17 to 0.20 ADA. Smart-contract transactions add a charge for memory and CPU execution units. The fee does not rise in an auction during congestion, so you see the exact fee before you sign.

The developer documentation gives the formula as fee = a x size(tx) + b and notes that both values are protocol parameters that can change through governance. Cardano’s own fee structure page explains that the fixed part is payable “regardless of the size of the transaction”.

Example: a 300-byte transfer would cost 44 x 300 + 155,381 = 168,581 lovelace, or about 0.169 ADA. Wallets often add a small safety margin, so the on-chain fee can be slightly higher than the formula.

What is the maximum supply of ADA?

The maximum supply of ADA is 45 billion. The ADA that was not distributed at launch sits in a reserve, and every epoch a fixed 0.3% of the remaining reserve is released to pay staking rewards, with 20% of that amount and of fees sent to the treasury. Because the release is a percentage of a shrinking reserve, issuance falls over time and never exceeds the cap.

The cap is stated on Kraken’s Cardano page, and the expansion rate (rho, 0.3%) and treasury rate (tau, 20%) are set out in Cardano’s monetary policy documentation, which estimates the reserve’s half-life at four to five years at that rate. The treasury funds development and community proposals through on-chain governance votes.

Compare this with Bitcoin’s 21 million cap and halvings and with Solana, which has no supply cap and issues SOL through a declining inflation rate.

How does staking ADA work?

You stake ADA by delegating your wallet’s stake to a stake pool. Your ADA never leaves your wallet and is never locked, so you can spend it at any time. Registering the stake key needs a 2 ADA refundable deposit. Delegation becomes active after 5 to 10 days, and rewards then arrive every five-day epoch, minus the pool’s fixed and percentage fees.

Cardano’s delegation documentation says “you can spend your ada normally at any time, regardless of how you delegated it”. Trezor’s Cardano staking guide gives the 2 ADA deposit, a staking fee of about 0.18 ADA and the 5 to 10 day activation window, and staking is done in the desktop Trezor Suite app.

The choice of pool matters: a pool that misses blocks or charges high fees pays less, and a heavily oversaturated pool pays proportionally less per ADA. Exchanges such as Kraken also offer ADA staking, but then the exchange holds your coins and eligibility varies by country.

How is Cardano governed?

Since 2024 and 2025, Cardano has on-chain governance: ADA holders delegate voting power to delegated representatives (DReps) or vote directly, and DReps, stake pool operators and a constitutional committee vote on protocol changes, hard forks and treasury withdrawals. The Chang upgrade introduced the first stage in August 2024, and the Plomin hard fork completed it on 29 January 2025.

Cardano’s documentation describes the Chang upgrade, which opened DRep registration, added PlutusV3 and set up an interim constitution and constitutional committee. The Plomin hard fork took effect at epoch 537 on 29 January 2025 and enabled the full set of CIP-1694 governance actions, including treasury withdrawals. A Cardano Constitutional Convention held from 4 to 6 December 2024 agreed the draft constitution with 95% of elected delegates in favour.

Has the Cardano network had outages or incidents?

Cardano’s most serious incident was a chain partition on 21 November 2025. A malformed delegation transaction exploited an old bug that newer node versions accepted and older ones rejected, so the network split into two chains. Block production continued on both, patched node software went out the same day, and the chains converged by 22 November. Several exchanges paused ADA deposits and withdrawals.

Intersect, the member organisation that coordinates Cardano development, published an incident report saying the partition began around 08:00 UTC, that “the network did not stall”, and that stake pool operators upgraded to node versions 10.5.2 and 10.5.3. Intersect said authorities including the FBI were being engaged.

The Block reported that Coinbase suspended ADA deposits and withdrawals for about 14 hours, from 12:15 UTC on 21 November to 02:10 UTC on 22 November, and that Kraken and other venues paused for shorter periods. If you were sending ADA that day, the transfer could have landed on the wrong chain and been reverted, which is why waiting for an all-clear during an incident is safer than retrying.

Which wallets support Cardano?

Popular Cardano wallets include Lace, built by Input Output Global as a browser extension and mobile app, Yoroi and Daedalus, plus Ledger and Trezor hardware wallets, which can stake ADA from their own apps. Download any wallet only from the vendor’s official domain, and never type your recovery phrase into a website, a support chat or a so-called wallet validation form.

Lace’s official site lists browser extensions for Chrome, Brave and Edge and mobile apps for iOS and Android. Ledger’s Cardano page says ADA can be staked in the Ledger Wallet app or delegated using Daedalus or Yoroi with a Ledger device. For a brand-by-brand hardware comparison, read Ledger vs Trezor vs Coldcard.

A long-running scam on Cardano is the fake “ADA giveaway”, where a video or post claims a founder will send back double whatever you send. No genuine project does this. Back up your phrase offline, as described in how to store a seed phrase.

Where can you buy ADA?

ADA is listed on most large exchanges, including Kraken, Coinbase and Binance. Kraken offers ADA spot buying from $10, selling to cash and ADA staking where it is eligible in your region. Which exchange you can use depends on where you live, so check the licensed entity for your country first, then move long-term holdings to your own wallet.

Our reviews cover each exchange’s licences, fees and restrictions: Kraken review, Coinbase review and Binance review (Binance does not serve US residents; Binance.US is a separate company). EU residents can compare platforms authorised under MiCA in crypto exchanges in Europe under MiCA. When withdrawing, choose the Cardano network and send a small test amount first, as explained in how to move crypto from an exchange to a wallet.

What are the main risks of Cardano?

The main risks are software bugs like the November 2025 chain partition, regulatory uncertainty, the influence of a few core development organisations, and scams targeting ADA holders. The SEC named ADA as a security in its June 2023 complaints against Binance and Coinbase; it dismissed the Coinbase case in February 2025 without ruling on the merits, so ADA’s legal status in the US has not been settled by a court.

• Regulatory status. The SEC’s complaint against Binance includes a section on ADA. The SEC dismissed its Coinbase case on 27 February 2025, saying the decision was not based on the merits of the claims.
• Software risk. The 2025 partition showed that a single malformed transaction can split the chain when node versions differ. Fixes came within hours, but exchanges froze transfers.
• Concentration. Input Output Global builds much of the core software and the Lace wallet. On-chain governance spreads decisions out, but development still depends on a small number of organisations.
• Custody and phishing. ADA left on an exchange depends on that exchange; see is it safe to keep crypto on an exchange.