Let me tell you a cold thing: neither CryptoPunks nor CryptoKitties stores metadata on the chain.
Original title: “Where does the NFT avatar you bought for tens of thousands of dollars exist? 》
Author: Block Rhythm
Regarding the NFT, which is currently hotly hyped in the market, whether the storage method of its pictures is decentralized and whether there is a risk of being tampered with after purchase is a question that many buyers are very concerned about. The metadata field in the NFT is generally used to store pictures. Therefore, we need a simple and efficient way to help users view the metadata in the NFT.
There are indeed some products that already provide certain metadata security assessment functions. For example, Opensea will show whether the metadata of the NFT is frozen. However, since the function names contained in the underlying smart contracts of various NFT projects are not completely the same, and the ways in which each project itself stores metadata are very different, a single query product is not compatible with all NFT products, and even May provide users with misleading information.
In this article, we will introduce users to a more general way of metadata verification, which is to verify directly through the blockchain browser.
Query the metadata of NFT in Etherscan
First of all, we need to make it clear that the uniqueness of NFTs that we say in daily life is determined by three basic elements. They are the public chain that deploys the NFT, the smart contract that generates the NFT, and the number of the NFT in the smart contract.
This article will take Ethereum, the most abundant NFT project at present, and NFT’s ERC-721 protocol as an example, to introduce readers to the method of querying NFT metadata through Etherscan.
First of all, readers can find the NFT collection page they wish to verify through the most commonly used Opensea. Taking a collection in Bored Ape Yacht Club as an example, you can see that the three most critical information of this NFT is indicated on the details page in the lower left corner:
- Contract address
2. The number of the NFT in the contract, which is the Token ID; - Where the public chain is, that is, Ethereum;
Click the link on the right side of the contract address, and the page will automatically jump to the Etherscan browser page corresponding to the contract address.
Click the Contract tab on the page to browse the underlying code of this contract.
We don’t need to understand the specific meaning of the code, just click on the Read Contract tab in the figure above to browse the queryable functions in this contract.
Find the function tokenURI that ranks 20th on the page. This is the special function for the NFT contract to query metadata.
Of course, the functions used to query metadata are named differently in different smart contracts, but they generally have fields such as URI and metadata, which require specific analysis. Fortunately, recent new projects will basically name this function tokenURI, which saves users a lot of trouble.
After clicking on the tokenURI function, we can see the following interface. Enter the NFT number we want to query in the upper input box, which is the Token ID number 6476 just seen in Opensea, and then click the query button Query below.
As you can see, after clicking the query button, the system returns a string of codes:
ipfs://QmeSjSinHpPnmXmspMjwiXyN6zS4E9zccariGR3jxcaWtq/6476
This string of codes is the metadata stored in the smart contract of NFT. It can be seen that the metadata of this NFT is stored as an ipfs storage link, so it can be judged that the NFT uses a decentralized storage method. Readers can use a browser that supports ipfs browsing, such as Brave, to view. This address returns the picture of the monkey represented by the NFT.
The above is the entire process of querying NFT metadata through Etherscan. It can be seen that there is actually no high threshold for users to operate. But the more critical question is, by understanding the metadata storage method of an NFT, what kind of help can it bring to future investment or purchase of NFT?
In the following, we will take several representative NFT projects as examples to introduce the metadata storage methods of mainstream NFT projects and their potential impact on the long-term value of NFTs.
Metadata storage methods of mainstream NFT projects
Don’t store
Yes, it is true that some NFT projects cannot find any information about the storage location of their pictures on the chain, and even the contract does not have a function to store metadata. This storage method was only used by certain fossil-level projects in the early days of NFT, and the most typical is CryptoPunks.
CryptoPunks
We inquired the contract address of CryptoPunks in the same way, and found that TokenURI or similar fields could not be found. But you can see that the fifth function imageHash returns a string of hash values, which is the hash value of a large image stitched together from the entire 10,000 CryptoPunk pictures. This picture is currently saved on the official website of the project ( picture link ). Users can download the picture by themselves and calculate its hash value and compare it with the hash value on the chain to verify the authenticity of the picture.
From this we can conclude that the CryptoPunks project does not store any pictures on the chain, but only provides users with a picture verification method in its smart contract. In essence, it does not store pictures, but only provides a way to verify on-chain.
Since there is no storage, after we purchase a CryptoPunks NFT, why can we accurately display the corresponding image on Opensea? In fact, this completely relies on the manual adaptation of websites such as Opensea on the front end of the web page. The CryptoPunks images are not stored on the chain, but in the centralized website cache. Therefore, the NFT of CryptoPunks must rely on a centralized organization to be displayed normally.
Therefore, the CryptoPunks NFT purchased by the investor is just a number in the smart contract, with neither pictures nor other practical functions. People’s recognition of him and the content of the pictures displayed on the website rely more on the consensus of the community. For example, for the second CryptoPunks NFT, whether it is the second one from left to right or the second one from top to bottom, the chain cannot provide a clear standard of judgment. Everyone just thinks that it is the representative according to habit. A certain avatar.
This type of NFT project has almost disappeared in the current market, because its existence and value require extremely strong community consensus support. If there are new projects that still use this “storage” method, investors are advised to purchase with caution.
CryptoKitties
CryptoKitties is also a NFT project with a long history. We also couldn’t find metadata in its contract, and the only function that resembled metadata returned a null value.
After analysis, we found that CryptoKitties also did not choose to store cat pictures on the chain, but saved the basic elements that make up cat images on a centralized official website. What is recorded on the chain is only the unique characteristic value of each cat, or it can be called the “gene” that determines the appearance of the cat. When the user purchases a CryptoKitty, the website responsible for the front-end display directly retrieves the characteristic genes of the NFT and generates a cat picture for display to the user according to the established rules.
Therefore, the storage method for the CryptoKitties project can be summarized as follows: the cat’s “gene” is stored on the chain, but the specific display content is synthesized by the server, and its display effect is completely dependent on the centralized server.
However, because CryptoKittiies is not a purely picture-based NFT project, its reproduction function can be synthesized only by the previous generation of “genes” and algorithms on the chain. The rarity of the cat’s appearance also depends solely on the composition of genes, so this project The lack of metadata will not have a significant impact on its game function and valuation.
The biggest advantage of the above two solutions to avoid the problem of metadata storage and solve the NFT front-end display problem through other workarounds is to save valuable on-chain storage space and reduce the complexity of project development. But the shortcomings are also obvious, because any website that wants to adapt or display related NFTs must manually configure and cache its display effect, and its final display effect is completely dependent on traditional centralized organizations. Once a key node fails, the NFT purchased by the user may not be displayed normally.
Of course, this kind of storage method is more in the early NFT projects, and the newly launched NFT projects have rarely adopted this kind of workaround.
On-chain storage
On-chain storage is also habitually referred to as “permanent storage”, because once a user submits data to the chain, relying on the immutable nature of the blockchain, the data on the chain is theoretically permanently stored. As long as we can expect this chain to run forever, then the corresponding data is equivalent to being permanently stored.
Currently, projects that use on-chain storage can also be divided into two categories, one is to store metadata on the same public chain of the NFT smart contract, and the other is to store on a dedicated storage public chain such as Arweave. There are not many typical projects currently using the second scheme, so this article will not introduce too much. The following only analyzes typical projects stored on Ethereum.
Autoglyphs
The Autoglyphs project was also developed by the Larva Labs team that developed CryptoPunks. Compared with CryptoPunks, this product is not so well-known, and its appearance is relatively simple. The figure below shows some of the product forms.
We still use the method mentioned above to call up its metadata through Etherscan, and the returned result is as shown below
It can be seen that the NFT picture elements of Autoglyphs are directly stored on Ethereum, but the position of the line break needs to be re-adjusted when displaying. Therefore, the display effect can be less affected by the front-end webpage, and the permanence and security of the stored data are better guaranteed. But at the same time, the shortcomings are also obvious, that is, the cost of on-chain storage in Ethereum is very expensive, and it is difficult to store more complex graphics.
Decentralized storage
The emergence of decentralized storage technology is much earlier than the invention of blockchain. Although decentralized storage has the same decentralized features as blockchain, decentralized storage cannot be directly equated with on-chain storage.
At present, the mainstream projects that use decentralized storage to store NFT metadata include the Bored Ape Yacht Club that has been introduced above, which is also the storage method used by most art NFTs at present.
The use of decentralized storage has the following significant advantages:
Non-tamperable: Since the domain name used to address the stored file contains the hash value of the file, it has the same non-tamperable feature as the blockchain, which is more in line with the original spirit of encryption;
Lower storage cost: For most of the current picture projects, basically a personal computer that can be connected to the Internet for a long time can ensure long-term storage of data. Even if a storage incentive layer such as filecoin combined with a blockchain incentive mechanism is used, the cost is still negligible compared to the cost of storage in Ethereum;
Of course, decentralized storage also has some shortcomings, that is, the permanence of data storage cannot be well guaranteed. For ipfs storage without filecoin incentive layer, once the nodes responsible for storage are all offline, the stored data may still be lost.
Centralized storage
The so-called centralized storage here is to store metadata in a centralized website server, and store the link to the website in the metadata. The following is an example of the Little Penguin project that has exploded in the past two days.
Pudgy Penguins
The following figure is a screenshot of the result returned by the tokenURI function query.
From the query results, it can be seen that the metadata of this project returns a centralized website link, indicating that the NFT image is directly stored on the server of the project’s official website. This storage method will face two major risks in the long run. One is that the data can be tampered with by the owner of the website, and the other is that the website may lose maintenance one day and the link cannot be accessed.
Therefore, for this type of image NFT project that uses a centralized storage method, investors need to carefully evaluate the strength of the project party and the willingness to maintain the operation of the project for a long time when purchasing. Since this type of NFT has no application value other than the picture itself, once the picture returned by the corresponding link is changed, the item may be reset at any time.
The immutability of the blockchain that people often say is only reflected in the URL link stored in the metadata. As for where this centralized URL link points, the blockchain has no knowledge of it and has no control at all. Therefore, this type of NFT is still centralized in terms of structure.
We can summarize it as a law, that is: the degree of decentralization of a product depends on the most centralized link of all its components. As long as one link adopts a centralized technology stack, then the entire product is a centralized The product. Therefore, image NFTs that use this type of storage method no longer have the basic characteristics of a decentralized and non-tamperable blockchain.
In other words, what everyone buys heavily is just a URL link fixed on the blockchain, not even a picture.
It doesn’t matter where it is stored
It doesn’t matter where it’s stored here, because the value of this type of NFT is not directly related to the way its metadata is stored. Even if these NFTs do not save or modify the metadata, they will not be Value has a significant impact. Below we take two well-known NFT projects as examples.
NFT in the Axie Infinity game
The following figure shows the content returned by querying a certain Axie NFT metadata. It can be seen that its metadata stores only a centralized URL link, so the front-end display picture is at risk of being tampered with.
However, unlike the image-based NFT, the main value of the NFT as a role or prop in the game does not come from the pictures that it can display on the front end of the webpage, but its functions and attributes in the game. For example, the higher the attack power of a game character represented by an NFT, the more likely it is to win the battle, and therefore the higher its value. The information stored in this NFT metadata is just similar to the skin of a game character, and its game attributes will not be affected even if it is modified.
This is similar to that in Glory of Kings, changing the skin of the game character will not have a significant impact on the operation of the game. Therefore, the NFT used in the game is more important to the actual function of the NFT in the game, or its intrinsic value, rather than the skin attributes that appear on the front end of the web page.
Uniswap V3 Position NFT
The storage method of Uniswap NFT metadata is extremely unique, and it is worthwhile to focus on it. Let’s first query the data on the chain through Etherscan, and the returned results are as follows:
It seems that the returned data is unreadable garbled, but the comment at the top provides us with the encoding method used: base64. We casually search for an online base64 decoding tool, which can parse the garbled code into the following readable results (due to too long, only part of the data is intercepted):
It can be seen that the token pair, market-making price range, token address, and statement of the market-making position are marked at the forefront of the metadata. In the image field at the back, the NFT image information stored in svg format is saved.
Here is a little explanation of the svg format. svg is a picture saving format, and its full Chinese name is “scalable vector graphics”. We know that the commonly used image saving format now is based on pixels. For example, our mobile phone photo saving format is to save the color of each pixel captured by the lens in the file one by one, so the higher the pixel, the clearer the picture. At the same time, the larger the storage space occupied, the more difficult it is to store on the chain.
The svg format does not store pictures by saving pixels, but saves the shape of graphics. For example: save a rectangle with an aspect ratio of 2:1, the background color is red, the name of the token pair is displayed in the upper left corner, and so on. The advantage of this way of storing images is that once the shape is determined, it can be zoomed in and out infinitely, and the storage space it occupies is not affected by the size of the graphics, but is only related to the complexity of the graphics. Therefore, this type of storage can help the low-cost storage structure of simple vector images on Ethereum.
And because Uniswap’s NFTs all use the same vector template, the image style of this NFT only needs to be stored once when the contract is deployed. After that, each newly minted NFT only needs to update the core information of the token in the graph. Can generate a new NFT picture. Therefore, the user does not need to pay storage costs for storing this picture.
Uniswap’s NFT metadata storage method can be said to be the most eye-catching solution among many NFT projects. He took care of several important needs at the same time. First, it is stored on the entire chain, which is completely decentralized and cannot be tampered with; the second is that all information can be read directly from the chain without relying on the cached data stored on the front end of the webpage; the third is that there is no risk of cross-chain calling data No need to worry about the failure or attack of the protocol that uses off-chain storage. As long as you trust the security of Ethereum, you can fully trust the security of the NFT. Fourth, more complex images can be saved, unlike the Autoglyphs project, which can only display simple graphic information.
Of course, after talking so much, we still have to return to the source of value of NFT in the end. In fact, for the value of Uniswap’s NFT, where the metadata is stored, or even whether the metadata is stored, does not affect its value at all. Because the value of Uniswap’s NFT depends only on the value of its assets that can be retrieved from the fund pool. Just like the bank certificate of deposit you hold, whether the printing quality is exquisite or rough, as long as you can retrieve the equivalent currency, the appearance of the certificate of deposit is completely irrelevant.
Finally, summarize the basic characteristics of Uniswap NFT. The front-end display picture of Uniswap’s NFT is stored on the Ethereum chain, which cannot be tampered with but can be upgraded by the team (see the figure below). According to its founder, the contract that stores metadata images is the only smart contract component in the entire Uniswap V3 smart contract group that can be upgraded later. However, no matter how the subsequent image changes, it will not affect the intrinsic value of its NFT.
The source of value of NFT assets
A research report once summarized NFT as a “container of metadata.” This extremely incisive summary explains the value source of the current art collection NFT. But for the above-mentioned applied NFT, this conclusion is difficult to give a reasonable explanation.
We believe that the current sources of value of NFT assets are mainly divided into two different types. One is to rely on the application value of the NFT itself, such as holding NFT to exchange certain assets, or having a certain attribute in the game that can increase the winning rate, or as an admission ticket for holding off-chain events, etc. The value of these NFTs comes from the use value they can bring to the holder.
The other is the value acquisition method of mainstream NFT projects. That is, NFT itself has no actual use value, and only relies on the displayed content such as pictures saved in the metadata to obtain a certain consensus (of course, some NFT projects do not even do this). This type of NFT has obvious air characteristics in the long run, and we believe that it will not be the mainstream NFT asset class in the future.
The large number of image-like NFT products currently popular, it is inevitable that people will recall the numerous air coin projects that have been flooding in 17 years. The project party only needs to copy and simply modify a version of the white paper, and can harvest a lot of wealth by issuing coins. The rise and fall of air currency prices are mainly determined by speculation, rather than its intrinsic use value.
Many current NFT projects have similar problems. The project team only needs to use algorithms to generate thousands of simple pictures, and they can get a lot of money through sales. There is almost no threshold for the operation of this kind of project, and there will only be more and more similar projects in the future, which will eventually make this round of NFT hype completely monetized.
Although the current hype phenomenon has improved ordinary users’ understanding of the concept of NFT, it has promoted the improvement of NFT-related infrastructure. However, due to its lack of long-term intrinsic value, in addition to a few early head projects, more image NFT projects will have a high risk of zeroing in the long run.
At the same time, users who purchase this type of image NFT need to pay special attention. Due to the way its metadata is stored, what you see in many NFT products is not equal to what you get. A large number of image-type NFT projects need to rely on a more centralized trading platform to “brainly supplement” the displayed pictures through manual methods. Once the maintenance of the Opensea platform is lost, many NFTs purchased by users will only be left with a string of URL links instead of pictures.
The future of NFT should rely more on application-based NFTs that are not affected by metadata. It can be seen that there are more and more explorations of such applications in the near future. For example, a recent project has cast a market-making algorithm into NFT. If users who use this algorithm in the future can pay a certain percentage to the NFT of this algorithm, the value of the NFT can be equal to the discount of its future cash flow, making it inherent Value is strongly supported. As for whether its metadata stores a cool image, I am afraid that no one will care about it anymore.
Currently, application-based NFTs with intrinsic value mainly exist in two tracks. One is a financial NFT, and the other is a game asset NFT. Both of these NFT assets have better long-term intrinsic value support. Their value no longer depends on the skin displayed on the front end of the web page such as metadata, but the actual use value brought to the owner. Compared with the current hotter image NFT, this application-based NFT is more likely to outperform the current hype cycle in the long run.
