What is the x402 protocol? How to ignite the revolution of online payment in the era of AI agents

The X402 protocol is regarded as the inscription of the AI era, which will change the way online payments are made, allowing AI to autonomously conduct economic activities and become the next foundational layer of Web3. This article is based on a piece written by Crypto Dog and organized, translated, and authored by Foresight News. (Background: How is the X402 protocol launched by Coinbase and Cloudflare reshaping the online payment revolution?) (Background Supplement: $PING hundredfold returns ignite the market, will the X402 protocol replicate the inscription craze?) The inscription (Ordinals/BRC20) has made countless people understand a truth: once a technical standard is activated, it can create a whole new wealth system. By 2025, this 'standard explosion' will occur again. The protagonist this time is the X402 protocol. It is 'the inscription of the AI era' and also the foundation of the next layer of Web3. Today, we will first explain 'what is X402', and next share how to participate in new projects. 1. The inscription changes 'storage', while X402 changes 'payment'. Let's recall the inscription craze from back then: The inscription (Ordinals) is the standard for 'writing text into Bitcoin transactions'; Anyone can use code to engrave data onto Bitcoin; It turns 'images, text, and tokens' into on-chain assets; Therefore, anyone can 'issue coins', leading to an explosive wealth effect. But the inscription only solves one problem: how to go on-chain (store value). The X402 solves another bigger problem: how to settle (transfer value). 2. What is X402? In one sentence: X402 is a web3 payment protocol that 'allows web pages, AI, and APIs to charge themselves'. Its principle is very simple: There is a rarely used status code in HTTP: 402 Payment Required. Coinbase revived it and redefined it as 'a native payment channel on the internet'. The process is as follows: 1⃣ You (or your AI) access a paid interface; 2⃣ The server returns a prompt: 'To use this service, please pay 0.05 USD USDC'; 3⃣ Payment completed → Automatically return results. The entire process does not require registration, log in, or a card. AI can spend money and buy services by itself. Just as the inscription is 'the switch to write data on-chain', X402 is 'the switch to write money on the internet'. 3. Why is it particularly important in the AI era? Because the main characters of the internet in the future will no longer be humans, but AI. AI will: Search for data, invoke models; Buy computing power, call interfaces; Even hire other AIs to do work for it. But the problem is that AI cannot swipe cards; it needs a payment method that machines can also understand, and X402 is that bridge. AI can automatically make payments (machine to machine); Supports micro-settlement (0.001 USD can also be paid); Supports cross-site and cross-service; All using stablecoins (USDC, NET Dollar). You can understand it as: 'HTTP allows web pages to communicate, X402 allows value to communicate.' 4. Why will it trigger a wealth effect? The reason for the popularity of the inscription in 2023 is — no one expected that a line of code could open a new economic system. Now, X402 follows the same logic. It is not a project, not an App, but a standard. Once the standard is universal, the whole world will build applications around it. Thus, a group of 'first wave Builders' quickly took off: Everyone's current mindset is very similar to that famous saying from 2023: 'When you don’t understand the inscription, it’s because you haven’t realized it is not an image, but a protocol.' Similarly, 'X402 is not a project, but a standard.' 5. The inscription relies on 'coin minting on-chain', while X402 relies on 'AI payment settlement'. The action of the inscription is: User → Initiate transaction → Write content into the block. The action of X402 is: AI → Initiate request → Automatically complete payment → Obtain data. Therefore: The inscription writes 'data', and X402 writes 'money flow'; The fuel of the inscription is 'speculation', and the fuel of X402 is 'real use'. The inscription ignites emotions, while X402 grows with applications. One is 'on-chain art', and the other is 'AI economy'. 6. What can ordinary people do? 1⃣ Understand the standard: X402 is not a coin, but a 'channel'. All AI, web pages, and APIs may connect to it in the future. 2⃣ Follow projects that are currently in use: $PING (minting verification) $SANTA (AI team collaboration) $AURA (AI backend) $MRDN (settlement) $PAYAI (payment channel) 3⃣ Pay attention to the volume of data and the number of transactions: Because this time the wealth comes not from speculation but from usage frequency. The more transactions, the more valuable the protocol. 7. In summary: The inscription of 2023 allowed humanity to inscribe value on-chain for the first time; The X402 of 2025 allows machines to pay value online for the first time. The inscription opened the era of 'everyone can issue assets', and X402 opens the era of 'AI can also participate in the economy'. This is the evolution from 'humans issuing coins' to 'AI making payments'. HTTP allows web pages to communicate, and X402 allows value to communicate. This wave is not a 'short-term hotspot', but a signal to activate 'a new layer of the internet'. 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