What is a Program
A program is essentially Solana's equivalent to a smart contract: code that gets deployed on-chain and triggers automatically when a transaction invokes it. That terminology difference isn't just cosmetic; the underlying architecture is fundamentally distinct. Where an Ethereum smart contract combines both logic and storage under a single address, Solana programs are stateless. The program's logic lives in one account, while every piece of data it manipulates lives in its own separate account, which the program itself controls.
A useful analogy is a laundromat. The machines don't come with pre-loaded clothes. Customers bring their own laundry, the machines do the work, and the user retrieves the clean clothes. A Solana program follows the same logic: the code is stored on-chain, but it contains no data. On each call, the user must explicitly pass every single account the program will interact with. The program modifies these accounts, and afterwards, the new state remains in them.
How Programs Work Technically
Programs are generally written in Rust and then compiled into sBPF bytecode, the instruction set interpreted by the Solana Virtual Machine. To deploy a program, you simply write that compiled code to an account and set that account as "executable." Once active, any transaction can execute the program by referencing its account address and providing any required accounts and instruction data.
Because this statelessness allows for massive code reusability, Solana developers don't typically deploy a contract for every use case. Consider the token situation on Ethereum: whenever you deploy a new ERC-20 token, the chain stores an entirely new copy of the contract's bytecode, resulting in many near-identical copies littering the blockchain. On Solana, the SPL Token program is a single instance that powers every single fungible token on the network. Adding a token merely involves creating a new mint account rather than deploying code. Solana applies a similar strategy to NFTs: nearly every collection traded on platforms like Magic Eden or Tensor relies on the same underlying Metaplex Token Metadata program.
Upgradeability represents a second core differentiator. On Ethereum, smart contracts are immutable by default; to allow upgrades, teams usually have to integrate a complex proxy pattern. On Solana, programs are upgradeable by default. They are associated with an upgrade authority account, which is a specific key permitted to swap out the program's bytecode. For example, the Jupiter router can have its logic updated at any time by the team, leaving all the existing user accounts intact. Of course, some teams may decide they need their programs to be permanent and so they deliberately burn this upgrade authority. These accounts are frozen and cannot be updated by anyone. You can view which Solana programs have been frozen through block explorers.
Why the Model Matters
This distinction matters to users because they interact with this model every day. Imagine you execute a swap on Jupiter using your Phantom wallet. This trade utilizes that single shared Jupiter program, where each side of your trade lives exclusively in accounts- your token accounts, the pool's token or SOL accounts, etc.- passed into that call. Because the data is external and fully declared before execution, it can be processed by Sealevel in parallel with other, unrelated transactions during a single 400-millisecond slot. In contrast, the EVM lacks that kind of pre-declared data, which is why Ethereum transactions are processed sequentially.
However, this model of default upgradeability involves some significant trade-offs with regards to security and trust. Since an upgrade authority is essentially a live admin key, whoever controls it can technically change the program's logic at any given time. While established teams, such as Orca and Kamino, generally secure this key behind a multisig or token-governed process, this does represent a lower bar of trust than the "code is law" approach of an immutable Ethereum contract; it matters to check who actually controls the upgrade keys. The use of Rust also increases the barrier to entry, as the security audit practices for Solana programs are different from the Solidity ecosystem and, currently, fewer auditors have this particular expertise.
On the other hand, this model allows for rapid patching of bugs and exploits. Should a security vulnerability ever be identified and discovered in a live Solana protocol, the developers can simply deploy an updated program in minutes. Teams running a live contract on Ethereum with an immutable upgrade authority cannot fix it on the fly; they can only warn users and attempt to secure the contract. Both models have undoubtedly lost funds and undoubtedly saved funds in various circumstances. For the Solana model, it really boils down to whether you trust mathematics or operational security.
Are Solana programs the same as smart contracts?
Programs are in the same category as smart contracts: on-chain, trustless code. The stateless model, default upgradeability, and sBPF bytecode are what makes the Solana developer experience distinct from Ethereum. Concepts translate reasonably well between the two ecosystems, but mechanics do not.
