Apple's event just ended. Half of my WeChat Moments are discussing the color of the new iPhone, and the other half—especially the ones who write code—are dropping links in group chats asking, "Anyone got a reliable UUID generator to recommend?" Outsiders look at this and think it's bizarre. What does the event have to do with UUIDs? Actually, it's not strange at all.
Every time Apple releases a new system or new hardware, developers have to scramble for a while. This year is especially rough. iOS 18 changed the underlying logic of privacy permissions. If an app wants to access certain device identifiers, it must go through a new authorization flow. In the past, many teams cut corners by directly using the device ID as the user's unique identifier. Now that path is completely blocked. What to do? You have no choice but to honestly generate a UUID, store it in the keychain, and use it as an anonymous user ID. So as soon as the event ended, search volume for UUID generators—a normally inconspicuous little tool—shot up more than tenfold.
UUID stands for Universally Unique Identifier. In plain terms, it's a string of characters that looks like gibberish, such as "550e8400-e29b-41d4-a716-446655440000." Its core value is two words: no duplicates. Theoretically, if you generate a hundred million per second for a hundred years straight, the chance of a collision is lower than getting hit by a meteorite. For developers, this thing is like issuing an ID card to data. Users, orders, logs, sessions—anything can get one.
But here's the problem: UUID generators are everywhere. Why did everyone suddenly start looking for them after Apple's event? Because this time there's a catch. iOS 18 has requirements for UUID versions. Version 4 must use a cryptographically secure random number generator and can no longer use ordinary pseudo-randomness. Some old tools generate UUIDs that look plausible, but the randomness source isn't strong enough, and Apple may reject them during review. On top of that, the new system changed keychain syncing. Under the same iCloud account, UUIDs need to stay consistent across devices, which means the generator must support exporting and importing keys. These details usually go unnoticed, but once everyone starts adapting after the event, they all surface at once.
I know an indie developer who makes a habit-tracking app. On the night of the event, he was complaining in a group chat that when the old version of his app ran on the new system, all user data got messed up. That's because the UUID generator he used before didn't account for iCloud syncing. After switching devices, a new ID was generated, and all check-in records were lost. He stayed up all night switching to an online tool that supports key export, migrating user data again, and didn't finish until 4 a.m. He said something pretty interesting: "Apple's event is the Spring Festival Gala for consumers and the final exam for developers."
So what tools do ordinary developers use now? From what I've observed, there are roughly three camps. One camp uses the command line. Linux and macOS come with uuidgen built in. Hit Enter and one pops out. Simple and brutal, but it can't batch generate, and cross-platform syncing isn't convenient. Another camp uses online tools. Open a webpage, click to generate, copy it, and leave. Good for temporary use, but you have to pick a reliable site. Some websites record the UUIDs you generate on the backend, which is basically letting user IDs run around naked. The third camp uses programming libraries—Python's uuid module, JavaScript's uuid package—integrated directly into code. That's the safest, but every time you need to generate one, you still have to run a script, which isn't very convenient during debugging.
So developers who really know what they're doing usually keep one or two bookmarks for online UUID generators on their phones, specifically choosing ones that generate purely on the front end, don't connect to the internet, support batch export, and let you choose the version. After Apple's event, traffic to these tools surged, not because everyone suddenly forgot how to write code, but because when adapting to the new system, they need to quickly verify, batch generate, and compare the effects of different versions. A friend of mine who does backend work told me he generated more than two thousand UUIDs with an online tool over the past couple of days just to test the new system's keychain syncing logic and see which ones would conflict.
In the end, a UUID generator is just a hammer. Usually it sits in the toolbox gathering dust. But once renovation starts, you find you need it everywhere. Apple's event is that renovation notice, telling developers: time to take out the hammer. And this renovation is no small matter. Privacy, syncing, and security are all changing at the same time. Nobody dares be careless. If you're a developer, or if you have developer friends, you'd better keep a reliable UUID generator handy these days too. Don't wait until your review gets rejected to start looking for one.
One last thing: be careful when choosing a tool. If it makes you log in as soon as you open it, or throws ads at you after generating, just close it. A good UUID generator should be like air. When you need it, it's there. When you don't, it doesn't bother you at all. Apple events happen every year, and developers' final exams happen every year too. Keeping a few handy little tools in your toolbox never hurts.