ERC721 vs. ERC721A

Maciej Zieliński

29 Mar 2022
ERC721 vs. ERC721A

Technology can be a great solution for many businesses and companies. Unfortunately, one of the unfortunate side effects is the amount of various technical jargon, which may be unintelligible to the average person. For the end-user, NFT often means little more than a decentralized collectors' item or a work of digital art. You can enjoy this industry without understanding how it works. But the trends in blockchain technology can be fascinating even for those who are not involved with creating it. Why are ERC721 and ERC721A so important in NFT? What makes it special and why should we learn about this technology? We're writing about this below!

What is ERC721?

Although blockchain technology is decentralized, we need a common language which will allow us to understand the data contained within it. As such, token standards like ERC721 become essential. It is a standard which works in a similar way to how all ports or plugs on various devices work. It is worth noting, for example, that formats such as PNG i JPEG, which are commonly associated with NFT, are by themselves image standards.
ERC721 is an extremely popular token standard for creating non-fungible tokens – NFT – on blockchains, such as Ethereum and Polygon. The letter ‘E’ in ‘ERC721’ stands for ‘Ethereum’ and is not the NFT standard that runs on blockchains that are incompatible with Ethereum portfolios such as Solana and Tezos.

​What makes ERC721 compliant tokens useful?

Below we outline some of the advantages of this solution:

  • Each token is unique (previously mentioned non-fungibility)
  • Each token can be transferred or sold
  • Owners can authorize other smart contracts to manage tokens

In addition, each of them is crucial to ensuring that NFT markets, such as OpenSea and LooksRare, can operate as intended. It should be pointed out that smart contracts are simply applications that live within blockchain technology. Seems complicated? It can be described in an even simpler way: ERC721 is a standardized way of creating unique blockchain tokens, which can be traded at markets.

​What is ERC721A?

Software developers in crypto typically use existing code libraries to simplify the development process of a project. When you write a code that's in the blockchain, there's even more pressure to use a battle-proven, existing code wherever possible, because blockchain technology prevents any code editing! In the NFT sector, a single open source code was widely accepted in order to enable the use of ERC721. Then there was the “Azuki” project, which quickly gained recognition in the NFT sector. In addition to the NFT issue itself, the project has created a new implementation of ERC721A.
The implementation of ERC721A is not meant to change the token standard. Its main purpose is to fit the token perfectly, but this task requires a number of other standards to be met, as opposed to ERC721 which has been used to date.
This has led to the reduction of the amount of gas needed to mint new NFT (especially those that are minted in batches).
The gas costs incurred in transferring NFT based on ERC721A to other persons at the original owner's prices are slightly higher. Overall, the gas savings that ERC721A can provide compared to ERC721 are excellent, but this solution cannot be implemented everywhere. For example, entities that do not mint NFT in bulk will still spend a significant amount of gas if we consider the transfer costs.

Let us remember that NFT provides many limitless possibilities not only for art, music, or sports. It is important to know and understand ERC721 and ERC721A, as this allows us to understand what NFT really is from its very basics. This makes us more aware of the direction in which this sector is developing. It is worth noting that while both implementations are important, they are neither the first nor last elements of NFT. They are the benchmark to follow.

How does ERC721A work?

ERC721A adopts specific conditions which then affect the smart contract project. This impact makes the following things happen:

  • Token IDs should always grow steadily – starting from zero. Currently, many NFT projects fulfill this condition.
  • The reduction of the gas costs related to minting NFT is the most important part of NFT production.

With these assumptions, ERC721A makes the following optimization of contracts:

  • Reduces the unused space, which is used to store metadata from tokens.
  • Limits ownership to one coin from the entire NFT batch.

Why is ERC721A so important?

Because it allows us to understand how high the gas charges really are, and what they result from! Reducing your work to sending transactions saves energy. At this point, we should emphasize that blockchain generates 2 types of transactions – reads and writes.

  • Write – occurs when we are doing something in a blockchain and its condition changes (for example, we sell NFT).
  • Read – it can be said that this is a review of the transaction file.

Users who use blockchain technology incur higher write costs than read costs. Therefore, if we reduce the pool of write information or transaction transfer requirements, we will reduce the cost of minting NFT.

What risks are involved with using ERC721A contracts for generating multiple NFT transactions?

TransferFrom and safeTransferFrom transactions cost more gas, which means that NFT can cost more from the moment of its minting. We should emphasize that using ERC721A leads to an increase in performance without the need to set owners of particular token ID.

For example, in the picture below there are two calls to mint a batch, one by Marcus to mint chips #100, #101, and #102 in one call, and the other by Brutus to mint chips #103 and #104

The above diagram shows that ERC721A must set up the property metadata twice, instead of 5 times – once for the Marcus package and once for the Brutus package. This is not so easy because by transferring a tokenID that does not have an owner address, the contract must create actions that include all tokenID’s in order to verify the original NFT owner. This is because the original owner has the right to move the token and set it to a new entity. Below we present a graph associated with this:

ERC721

The method of reading this chart is as follows: first move to the x-axis and then to the y-axis, for example:

  • „Mint a batch of 1 NFT, and then transfer tokenID 0”,
  • „Mint a batch 3 of NFT, and then transfer tokenID 1”
  • „Mint a batch 5 of NFT, and then transfer tokenID 4”

The above results indicate that moving token IDs in the middle of a larger mint batch (i.e. t1, t2) costs more than moving token IDs at the end of the batch (i.e. t0, t4).

How to minimize the cost of transferring an entire batch of NFT?

You can minimize costs if you are always minting the maximum allowed number of NFT when releasing an entire batch. In addition – when moving a batch, it is important to start a cycle with tokens of an ODD number in an ascending manner.
Examples of NFT projects using the ERC721A contract
Here is a list of projects, which are currently using the ERC721A contract:

  • @AzukiZen
  • @cerealclubnft
  • @TheLostGlitches
  • @standardweb3
  • @KittyCryptoGang
  • @XRabbitsClub
  • @WhaleTogether
  • @pixelpiracynft
  • @dastardlyducks
  • @MissMetaNFT
  • @StarcatchersNFT
  • @LivesOfAsuna
  • @richsadcatnft
  • @themonkeypoly
  • @womenofcrypto_
  • @TravelToucans
  • @HuhuNFT

Are ERC721A contracts still considered to be NFT transactions?

Of course. ERC721A contracts are NFT. Any contract that implements the ERC721 token standard, or the ERC1155 interfaces is seen as non-fungible or semi-fungible tokens. To put it simply, ERC721A is an extension and optimization of the previous version, the ERC721. The ERC721A contract is a very good idea which allows for saving money on gas in a given community, while at the same time protecting the Ethereum network from unnecessary workload.

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AI-Driven Frontend Automation: Elevating Developer Productivity to New Heights

Gracjan Prusik

11 Mar 2025
AI-Driven Frontend Automation: Elevating Developer Productivity to New Heights

AI Revolution in the Frontend Developer's Workshop

In today's world, programming without AI support means giving up a powerful tool that radically increases a developer's productivity and efficiency. For the modern developer, AI in frontend automation is not just a curiosity, but a key tool that enhances productivity. From automatically generating components, to refactoring, and testing – AI tools are fundamentally changing our daily work, allowing us to focus on the creative aspects of programming instead of the tedious task of writing repetitive code. In this article, I will show how these tools are most commonly used to work faster, smarter, and with greater satisfaction.

This post kicks off a series dedicated to the use of AI in frontend automation, where we will analyze and discuss specific tools, techniques, and practical use cases of AI that help developers in their everyday tasks.

AI in Frontend Automation – How It Helps with Code Refactoring

One of the most common uses of AI is improving code quality and finding errors. These tools can analyze code and suggest optimizations. As a result, we will be able to write code much faster and significantly reduce the risk of human error.

How AI Saves Us from Frustrating Bugs

Imagine this situation: you spend hours debugging an application, not understanding why data isn't being fetched. Everything seems correct, the syntax is fine, yet something isn't working. Often, the problem lies in small details that are hard to catch when reviewing the code.

Let’s take a look at an example:

function fetchData() {
    fetch("htts://jsonplaceholder.typicode.com/posts")
      .then((response) => response.json())
      .then((data) => console.log(data))
      .catch((error) => console.error(error));
}

At first glance, the code looks correct. However, upon running it, no data is retrieved. Why? There’s a typo in the URL – "htts" instead of "https." This is a classic example of an error that could cost a developer hours of frustrating debugging.

When we ask AI to refactor this code, not only will we receive a more readable version using newer patterns (async/await), but also – and most importantly – AI will automatically detect and fix the typo in the URL:

async function fetchPosts() {
    try {
      const response = await fetch(
        "https://jsonplaceholder.typicode.com/posts"
      );
      const data = await response.json();
      console.log(data);
    } catch (error) {
      console.error(error);
    }
}

How AI in Frontend Automation Speeds Up UI Creation

One of the most obvious applications of AI in frontend development is generating UI components. Tools like GitHub Copilot, ChatGPT, or Claude can generate component code based on a short description or an image provided to them.

With these tools, we can create complex user interfaces in just a few seconds. Generating a complete, functional UI component often takes less than a minute. Furthermore, the generated code is typically error-free, includes appropriate animations, and is fully responsive, adapting to different screen sizes. It is important to describe exactly what we expect.

Here’s a view generated by Claude after entering the request: “Based on the loaded data, display posts. The page should be responsive. The main colors are: #CCFF89, #151515, and #E4E4E4.”

Generated posts view

AI in Code Analysis and Understanding

AI can analyze existing code and help understand it, which is particularly useful in large, complex projects or code written by someone else.

Example: Generating a summary of a function's behavior

Let’s assume we have a function for processing user data, the workings of which we don’t understand at first glance. AI can analyze the code and generate a readable explanation:

function processUserData(users) {
  return users
    .filter(user => user.isActive) // Checks the `isActive` value for each user and keeps only the objects where `isActive` is true
    .map(user => ({ 
      id: user.id, // Retrieves the `id` value from each user object
      name: `${user.firstName} ${user.lastName}`, // Creates a new string by combining `firstName` and `lastName`
      email: user.email.toLowerCase(), // Converts the email address to lowercase
    }));
}

In this case, AI not only summarizes the code's functionality but also breaks down individual operations into easier-to-understand segments.

AI in Frontend Automation – Translations and Error Detection

Every frontend developer knows that programming isn’t just about creatively building interfaces—it also involves many repetitive, tedious tasks. One of these is implementing translations for multilingual applications (i18n). Adding translations for each key in JSON files and then verifying them can be time-consuming and error-prone.

However, AI can significantly speed up this process. Using ChatGPT, DeepSeek, or Claude allows for automatic generation of translations for the user interface, as well as detecting linguistic and stylistic errors.

Example:

We have a translation file in JSON format:

{
  "welcome_message": "Welcome to our application!",
  "logout_button": "Log out",
  "error_message": "Something went wrong. Please try again later."
}

AI can automatically generate its Polish version:

{
  "welcome_message": "Witaj w naszej aplikacji!",
  "logout_button": "Wyloguj się",
  "error_message": "Coś poszło nie tak. Spróbuj ponownie później."
}

Moreover, AI can detect spelling errors or inconsistencies in translations. For example, if one part of the application uses "Log out" and another says "Exit," AI can suggest unifying the terminology.

This type of automation not only saves time but also minimizes the risk of human errors. And this is just one example – AI also assists in generating documentation, writing tests, and optimizing performance, which we will discuss in upcoming articles.

Summary

Artificial intelligence is transforming the way frontend developers work daily. From generating components and refactoring code to detecting errors, automating testing, and documentation—AI significantly accelerates and streamlines the development process. Without these tools, we would lose a lot of valuable time, which we certainly want to avoid.

In the next parts of this series, we will cover topics such as:

Stay tuned to keep up with the latest insights!

The Ultimate Web3 Backend Guide: Supercharge dApps with APIs

Tomasz Dybowski

04 Mar 2025
The Ultimate Web3 Backend Guide: Supercharge dApps with APIs

Introduction

Web3 backend development is essential for building scalable, efficient and decentralized applications (dApps) on EVM-compatible blockchains like Ethereum, Polygon, and Base. A robust Web3 backend enables off-chain computations, efficient data management and better security, ensuring seamless interaction between smart contracts, databases and frontend applications.

Unlike traditional Web2 applications that rely entirely on centralized servers, Web3 applications aim to minimize reliance on centralized entities. However, full decentralization isn't always possible or practical, especially when it comes to high-performance requirements, user authentication or storing large datasets. A well-structured backend in Web3 ensures that these limitations are addressed, allowing for a seamless user experience while maintaining decentralization where it matters most.

Furthermore, dApps require efficient backend solutions to handle real-time data processing, reduce latency, and provide smooth user interactions. Without a well-integrated backend, users may experience delays in transactions, inconsistencies in data retrieval, and inefficiencies in accessing decentralized services. Consequently, Web3 backend development is a crucial component in ensuring a balance between decentralization, security, and functionality.

This article explores:

  • When and why Web3 dApps need a backend
  • Why not all applications should be fully on-chain
  • Architecture examples of hybrid dApps
  • A comparison between APIs and blockchain-based logic

This post kicks off a Web3 backend development series, where we focus on the technical aspects of implementing Web3 backend solutions for decentralized applications.

Why Do Some Web3 Projects Need a Backend?

Web3 applications seek to achieve decentralization, but real-world constraints often necessitate hybrid architectures that include both on-chain and off-chain components. While decentralized smart contracts provide trustless execution, they come with significant limitations, such as high gas fees, slow transaction finality, and the inability to store large amounts of data. A backend helps address these challenges by handling logic and data management more efficiently while still ensuring that core transactions remain secure and verifiable on-chain.

Moreover, Web3 applications must consider user experience. Fully decentralized applications often struggle with slow transaction speeds, which can negatively impact usability. A hybrid backend allows for pre-processing operations off-chain while committing final results to the blockchain. This ensures that users experience fast and responsive interactions without compromising security and transparency.

While decentralization is a core principle of blockchain technology, many dApps still rely on a Web2-style backend for practical reasons:

1. Performance & Scalability in Web3 Backend Development

  • Smart contracts are expensive to execute and require gas fees for every interaction.
  • Offloading non-essential computations to a backend reduces costs and improves performance.
  • Caching and load balancing mechanisms in traditional backends ensure smooth dApp performance and improve response times for dApp users.
  • Event-driven architectures using tools like Redis or Kafka can help manage asynchronous data processing efficiently.

2. Web3 APIs for Data Storage and Off-Chain Access

  • Storing large amounts of data on-chain is impractical due to high costs.
  • APIs allow dApps to store & fetch off-chain data (e.g. user profiles, transaction history).
  • Decentralized storage solutions like IPFS, Arweave and Filecoin can be used for storing immutable data (e.g. NFT metadata), but a Web2 backend helps with indexing and querying structured data efficiently.

3. Advanced Logic & Data Aggregation in Web3 Backend

  • Some dApps need complex business logic that is inefficient or impossible to implement in a smart contract.
  • Backend APIs allow for data aggregation from multiple sources, including oracles (e.g. Chainlink) and off-chain databases.
  • Middleware solutions like The Graph help in indexing blockchain data efficiently, reducing the need for on-chain computation.

4. User Authentication & Role Management in Web3 dApps

  • Many applications require user logins, permissions or KYC compliance.
  • Blockchain does not natively support session-based authentication, requiring a backend for handling this logic.
  • Tools like Firebase Auth, Auth0 or Web3Auth can be used to integrate seamless authentication for Web3 applications.

5. Cost Optimization with Web3 APIs

  • Every change in a smart contract requires a new audit, costing tens of thousands of dollars.
  • By handling logic off-chain where possible, projects can minimize expensive redeployments.
  • Using layer 2 solutions like Optimism, Arbitrum and zkSync can significantly reduce gas costs.

Web3 Backend Development: Tools and Technologies

A modern Web3 backend integrates multiple tools to handle smart contract interactions, data storage, and security. Understanding these tools is crucial to developing a scalable and efficient backend for dApps. Without the right stack, developers may face inefficiencies, security risks, and scaling challenges that limit the adoption of their Web3 applications.

Unlike traditional backend development, Web3 requires additional considerations, such as decentralized authentication, smart contract integration, and secure data management across both on-chain and off-chain environments.

Here’s an overview of the essential Web3 backend tech stack:

1. API Development for Web3 Backend Services

  • Node.js is the go-to backend runtime good for Web3 applications due to its asynchronous event-driven architecture.
  • NestJS is a framework built on top of Node.js, providing modular architecture and TypeScript support for structured backend development.

2. Smart Contract Interaction Libraries for Web3 Backend

  • Ethers.js and Web3.js are TypeScript/JavaScript libraries used for interacting with Ethereum-compatible blockchains.

3. Database Solutions for Web3 Backend

  • PostgreSQL: Structured database used for storing off-chain transactional data.
  • MongoDB: NoSQL database for flexible schema data storage.
  • Firebase: A set of tools used, among other things, for user authentication.
  • The Graph: Decentralized indexing protocol used to query blockchain data efficiently.

4. Cloud Services and Hosting for Web3 APIs

When It Doesn't Make Sense to Go Fully On-Chain

Decentralization is valuable, but it comes at a cost. Fully on-chain applications suffer from performance limitations, high costs and slow execution speeds. For many use cases, a hybrid Web3 architecture that utilizes a mix of blockchain-based and off-chain components provides a more scalable and cost-effective solution.

In some cases, forcing full decentralization is unnecessary and inefficient. A hybrid Web3 architecture balances decentralization and practicality by allowing non-essential logic and data storage to be handled off-chain while maintaining trustless and verifiable interactions on-chain.

The key challenge when designing a hybrid Web3 backend is ensuring that off-chain computations remain auditable and transparent. This can be achieved through cryptographic proofs, hash commitments and off-chain data attestations that anchor trust into the blockchain while improving efficiency.

For example, Optimistic Rollups and ZK-Rollups allow computations to happen off-chain while only submitting finalized data to Ethereum, reducing fees and increasing throughput. Similarly, state channels enable fast, low-cost transactions that only require occasional settlement on-chain.

A well-balanced Web3 backend architecture ensures that critical dApp functionalities remain decentralized while offloading resource-intensive tasks to off-chain systems. This makes applications cheaper, faster and more user-friendly while still adhering to blockchain's principles of transparency and security.

Example: NFT-based Game with Off-Chain Logic

Imagine a Web3 game where users buy, trade and battle NFT-based characters. While asset ownership should be on-chain, other elements like:

  • Game logic (e.g., matchmaking, leaderboard calculations)
  • User profiles & stats
  • Off-chain notifications

can be handled off-chain to improve speed and cost-effectiveness.

Architecture Diagram

Below is an example diagram showing how a hybrid Web3 application splits responsibilities between backend and blockchain components.

Hybrid Web3 Architecture

Comparing Web3 Backend APIs vs. Blockchain-Based Logic

FeatureWeb3 Backend (API)Blockchain (Smart Contracts)
Change ManagementCan be updated easilyEvery change requires a new contract deployment
CostTraditional hosting feesHigh gas fees + costly audits
Data StorageCan store large datasetsLimited and expensive storage
SecuritySecure but relies on centralized infrastructureFully decentralized & trustless
PerformanceFast response timesLimited by blockchain throughput

Reducing Web3 Costs with AI Smart Contract Audit

One of the biggest pain points in Web3 development is the cost of smart contract audits. Each change to the contract code requires a new audit, often costing tens of thousands of dollars.

To address this issue, Nextrope is developing an AI-powered smart contract auditing tool, which:

  • Reduces audit costs by automating code analysis.
  • Speeds up development cycles by catching vulnerabilities early.
  • Improves security by providing quick feedback.

This AI-powered solution will be a game-changer for the industry, making smart contract development more cost-effective and accessible.

Conclusion

Web3 backend development plays a crucial role in scalable and efficient dApps. While full decentralization is ideal in some cases, many projects benefit from a hybrid architecture, where off-chain components optimize performance, reduce costs and improve user experience.

In future posts in this Web3 backend series, we’ll explore specific implementation details, including:

  • How to design a Web3 API for dApps
  • Best practices for integrating backend services
  • Security challenges and solutions

Stay tuned for the next article in this series!