Solana has emerged as one of the most high-performance blockchain platforms, known for its speed, scalability, and low transaction costs. At the heart of its ecosystem are programs—the equivalent of smart contracts on other blockchains like Ethereum. These programs power decentralized applications (dApps), token systems, DeFi protocols, and more.
Understanding how Solana programs work is essential for any developer looking to build on this fast-growing network.
What Are Solana Programs?
On Solana, what other blockchains call "smart contracts" are referred to as programs. These are stateless, immutable pieces of executable code deployed directly onto the blockchain. Once deployed, users interact with them by sending transactions that contain specific instructions telling the program what action to perform.
Key characteristics of Solana programs:
- They reside in on-chain accounts containing compiled executable binaries.
- Programs are stateless, meaning they don’t store data themselves but can read from and write to separate data accounts.
- Each program is organized into functions called instructions, which define the actions it can perform.
- Programs can be upgradable if an upgrade authority is assigned during deployment. Once this authority is removed, the program becomes immutable.
- Verifiable builds allow users to confirm that a program’s on-chain bytecode matches its public source code—ensuring transparency and trust.
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Writing Solana Programs: Rust and Frameworks
The vast majority of Solana programs are written in Rust, a systems programming language known for safety, performance, and concurrency—ideal traits for secure blockchain development.
There are two primary approaches to writing Solana programs:
1. Anchor Framework
Anchor is the most popular framework for building Solana programs. It simplifies development by:
- Automatically generating boilerplate code using Rust macros.
- Providing built-in security checks and error handling.
- Enabling easier testing and integration with frontends.
For newcomers, Anchor is highly recommended as it significantly reduces complexity while maintaining flexibility.
2. Native Rust
Developing in native Rust means writing programs directly using Solana’s SDK without any abstraction layer. This approach offers:
- Full control over program logic and resource management.
- Greater optimization potential.
- Steeper learning curve due to increased boilerplate and manual account validation.
While powerful, native development is best suited for experienced developers who need fine-grained control.
Program Deployment and Upgradability
When a program is deployed on Solana, it's stored in an executable account. The deployment process involves several steps:
- Compiling the Rust code into eBPF-compatible bytecode (specifically Solana’s sBPF format).
- Uploading the binary to a buffer account.
- Deploying it via a loader program.
Each program has an upgrade authority—an account authorized to modify or update the program after deployment. This enables bug fixes and feature enhancements post-launch.
However, once the upgrade authority is revoked (set to None), the program becomes permanently immutable, ensuring long-term trust and predictability.
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Ensuring Trust: Verifiable Builds
One of the biggest concerns in decentralized systems is whether deployed code matches its published source. To address this, Solana supports verifiable builds—a process where anyone can verify that an on-chain program’s binary corresponds exactly to its open-source code.
Tools and practices include:
- Solana Verifiable Build CLI by Ellipsis Labs: Allows independent verification of program binaries against source code.
- Anchor’s built-in support: Anchor natively integrates verifiable build workflows, making it easier for developers to publish auditable programs.
- Verification via explorers: Users can check program status on tools like Solana Explorer—verified programs display a clear indicator.
Example: View a verified program on Solana Explorer to see how transparency is implemented in practice.
How Programs Are Compiled: From Rust to sBPF
Solana uses the LLVM compiler infrastructure to compile Rust code into ELF (Executable and Linkable Format) files. These contain Solana Bytecode Format (sBPF)—a customized version of eBPF optimized for blockchain execution.
This compiled ELF file is then deployed on-chain and executed by the Solana runtime when transactions invoke its instructions.
Loader Programs: Managing Executable Accounts
Every Solana program is owned by a loader program, responsible for deploying, upgrading, and managing executable accounts. There are currently five loader types:
- Native Loader: Owns all other loaders.
- BPF Loader v1 & v2: Legacy loaders; management instructions disabled but still support execution.
- BPF Loader v3: Upgradeable but being phased out.
- Loader v4: The future standard, designed for better efficiency and security in managing upgradable programs.
These loaders enable critical operations such as:
- Deploying new programs
- Upgrading existing ones
- Transferring ownership
- Finalizing immutable programs
Loader v4 is expected to become the default due to improved design and long-term maintainability.
Precompiled Programs: Optimized On-Chain Verification
Solana includes several precompiled programs that offer efficient cryptographic operations at the protocol level:
Ed25519 Program
- Program ID:
Ed25519SigVerify111111111111111111111111111 - Purpose: Verifies Ed25519 digital signatures.
- Use case: Enables efficient signature validation within transactions.
Secp256k1 Program
- Program ID:
KeccakSecp256k11111111111111111111111111111 - Purpose: Recovers public keys from ECDSA signatures (similar to Ethereum’s
ecrecover). - Use case: Cross-chain message verification and wallet compatibility.
Secp256r1 Program
- Program ID:
Secp256r1SigVerify1111111111111111111111111 - Purpose: Validates up to 8 secp256r1 signatures per instruction.
- Note: Enforces low-S values to prevent signature malleability.
These precompiled programs reduce computational overhead by executing complex crypto operations natively within the runtime.
Core Programs: Foundation of the Network
Solana ships with several core programs that provide essential functionality across the network:
| Program | Function |
|---|---|
| System Program | Manages account creation, fund transfers, and allocations. |
| Vote Program | Handles validator voting and consensus participation. |
| Stake Program | Manages staking delegations and reward distribution. |
| Config Program | Stores configuration data with access-controlled updates. |
| Compute Budget Program | Sets compute limits and prioritization fees for transactions. |
| Address Lookup Table Program | Enables larger transactions by expanding account references. |
| ZK ElGamal Proof Program | Supports zero-knowledge proofs for encrypted data operations. |
These programs are foundational—developers interact with them regularly when building dApps or managing network resources.
Frequently Asked Questions (FAQ)
What is a Solana program?
A Solana program is a stateless, executable piece of code deployed on-chain that processes instructions from transactions. It's equivalent to a smart contract on other blockchains.
Can Solana programs store data?
No, programs themselves are stateless. However, they can create and modify separate data accounts to persist information.
How do I verify a program’s source code?
You can use tools like the Solana Verifiable Build CLI or check verification status on explorers like Solana Explorer.
Is Rust the only language for Solana programs?
While Rust is the primary language, experimental support exists for C/C++ via LLVM. However, Rust remains the standard due to safety and ecosystem maturity.
What happens if I lose upgrade authority?
If you revoke or lose access to the upgrade authority, the program becomes immutable—no further changes can be made.
Why use Anchor over native Rust?
Anchor reduces boilerplate, improves security through automatic checks, and streamlines testing—making it ideal for faster, safer development.
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Final Thoughts
Solana programs represent a powerful paradigm in decentralized computing—combining high performance with developer flexibility. Whether you're building DeFi protocols, NFT marketplaces, or cross-chain bridges, understanding how programs work—from compilation to verification—is key to success.
With robust tooling like Anchor, verifiable builds, and efficient precompiled libraries, Solana continues to empower developers to create secure, scalable, and transparent applications.
By mastering these concepts, you position yourself at the forefront of blockchain innovation—ready to build the future of web3.