A developer can create and test a basic NFT contract by implementing ERC-721 token identity, defining who may mint and how token IDs are assigned, exposing metadata references, and checking the intended behavior in a test environment. The available evidence supports core ERC-721 identity and metadata concepts, but does not verify a particular Solidity compiler version, dependency version, safe-mint API, or runnable code sample. This guide therefore provides a concrete implementation and test workflow without presenting unverified code as compile-ready or production-safe.

What a basic ERC-721 contract needs

ERC-721 is a standard for individually distinguishable tokens. On an Ethereum chain, a token is uniquely identified by the combination of its smart-contract address and token ID. A token ID is not a universal identifier by itself: the contract address is part of the identity. source

A contract manages token records and the rules for ownership and transfer. Minting creates a token record and assigns its initial ownership under the contract’s rules. That operation does not, by itself, create, authenticate, store, or transfer rights in the work or asset the token refers to. source

A contract may associate a token ID with a metadata URI. A URI is a reference to metadata, not the metadata itself and not proof that the referenced material will remain available, accurate, permanent, or licensed. source

This distinction sets the scope of a basic implementation: the contract defines token identity and behavior; metadata describes or points to an associated subject; other systems and terms determine what the association means. ERC-721 supports standardized ownership and transfer records for distinct token IDs that applications can associate with digital or physical subjects, but the standard does not establish the subject’s authenticity. source

Treat a minimal contract as an educational starting point, not a security conclusion. The evidence available for this guide does not establish a specific compiler release, library version, or complete sample implementation. It would therefore be misleading to provide an inheritance statement or function call as if it were verified against a particular dependency.

Create NFT Solidity: define the contract and minting rules

Before implementing a contract, document the decisions that determine its behavior:

  1. Token identity: Choose how the contract assigns IDs and how it handles a repeated or invalid ID. The ERC-721 identity is the contract address together with the ID, so an ID alone does not identify a token across contracts. source
  2. Mint authority: Decide which account or process may create token records. Minting follows the contract’s rules; the evidence here does not prescribe a particular access-control design or show that one design is sufficient. source
  3. Recipient handling: Define who receives initial ownership and what recipient cases are allowed. Verify the exact behavior in the selected ERC-721 implementation’s documentation rather than inferring it from a method name.
  4. Metadata policy: Decide whether the contract exposes a URI for each token and how it determines that URI. The URI reference does not guarantee the availability or correctness of its target. source

A common structure for this kind of contract is an ERC-721-compatible implementation plus collection-level information, token-ID logic, a mint rule, and metadata behavior. Those are design responsibilities, not a verified Solidity code recipe. To turn them into code, select an implementation and consult its official documentation for the exact version and API. The allowed evidence does not establish a compatible compiler pragma, dependency release, or safe-mint function signature, so this guide does not invent one.

In particular, “safe mint” should not be treated as a general security promise. The available evidence does not define its precise behavior or establish what a chosen library’s implementation does when minting to a recipient. Check the selected version’s documentation and tests for the recipient-handling behavior and any external interactions. If the behavior cannot be verified for that version, do not rely on a guessed method name or signature.

Record the selected compiler and dependency versions in the project’s build configuration and confirm compatibility using the documentation for those versions. A version label alone does not prove the contract compiles, behaves as intended, or is secure. The build should be reproducible enough for reviewers to identify which implementation and compiler settings the code uses; the evidence here does not support naming specific settings or versions.

Connect token IDs to metadata

An ERC-721 metadata extension can expose a token URI associated with a particular token ID. At a conceptual level, a project may construct references from a shared base URI and token-specific information, or configure a separate URI for each token. These are implementation choices, not a rule that applies to every collection. source

For a fixed-base approach, the contract’s behavior determines how a token ID contributes to the final reference. For a per-token approach, the contract or related logic must determine which reference is associated with each ID. In both cases, review the actual URI returned for a token instead of assuming that the intended pattern was implemented correctly.

The URI-to-content relationship also has a limit: the standard does not guarantee the availability, permanence, accuracy, or licensing of the referenced content. A contract can expose a reference without proving that the target will continue to resolve or that its contents match the project’s expectations. source

A useful review sequence is to identify a token by its contract address and ID, determine the URI the contract exposes for that ID, and compare the result with the project’s intended metadata reference. This checks the association at the time of review. It does not establish future availability or validate rights in the referenced material.

Compile and test the NFT contract

Keep test expectations tied to the exact implementation and build inputs. A test workflow can proceed in stages:

  1. Confirm the inputs. Record the Solidity compiler and ERC-721 dependency versions. Consult their corresponding official documentation for supported syntax and APIs. The evidence available here does not verify particular versions or provide a compile-ready command.
  2. Test a permitted mint. Check that the contract creates the intended ID and assigns initial ownership to the intended recipient under its implemented rules. Confirm the contract address and ID used to identify the resulting token. source
  3. Test ID behavior. Exercise the contract’s intended handling of repeated IDs and other invalid ID cases. The identity definition does not prescribe an ID-generation strategy; verify the specific strategy the contract implements. source
  4. Test mint permissions. If minting is restricted, attempt the operation through an account that is not meant to have that authority and check the implemented rule. The evidence does not provide a permission pattern, so the test must reflect the project’s actual design.
  5. Test metadata output. For a minted token, inspect the URI the contract exposes and compare it with the expected reference. This tests the URI association, not the persistence, accuracy, or licensing of the referenced content. source
  6. Test recipient and failure cases. Use the selected implementation’s documentation to determine relevant recipient cases and expected failure behavior. Do not infer safe-mint behavior from a function name or copy an API from a different version.

Run these checks in a local or other non-production test environment before considering deployment. The results show only what was exercised under the chosen test conditions; they do not prove that every execution path is correct or secure. This guide does not claim that the sample code has been compiled or that any tests have been run.

Review the contract before deployment

Before making a deployment decision, review the concrete rules that affect token creation and metadata:

  • Which accounts or processes can mint, and what happens when an unauthorized account tries?
  • How are IDs assigned, and how does the implementation handle repeated or invalid IDs?
  • What recipient behavior does the selected implementation use, including any behavior described as safe minting?
  • How is a URI determined for each token, and does the returned reference match the intended association?
  • Which compiler and dependency versions were used, and do the project’s documentation and build configuration identify them?

Keep the limits of those checks explicit. ERC-721 identity is based on a contract address and token ID; the token record does not by itself establish the meaning or authenticity of the referenced subject. Minting creates a token record and initial ownership according to contract rules, but does not itself create, authenticate, store, or transfer rights in the referenced asset. source source A URI likewise does not guarantee that its content remains accessible or correct. source

A structured verification framework can help organize review. The OWASP Smart Contract Security Verification Standard provides a framework for designing, building, and testing EVM-based smart contracts and decentralized applications. Its published version is early and should be supplemented with project-specific threat modeling and review; using a framework is not a security guarantee. source

The practical boundary of this guide is implementation and validation: define token identity and mint rules, connect each token ID to the intended metadata reference, verify the selected implementation’s documented APIs and versions, and test expected behavior before considering deployment. It does not select a marketplace or provider, advise on promotion or pricing, or determine legal or tax treatment.

Sources and references