What the new iPhone update does
Each iPhone update patches security holes, adds features to existing apps, and sometimes changes how your phone looks or behaves. The specific changes depend on which version you have and which update you're installing — a major update (like iOS 17 to iOS 18) brings bigger changes than a minor one (like iOS 18.0 to iOS 18.1). Apple releases updates roughly every month, with larger versions once a year in the fall.
The security patches are the reason to install updates promptly. They close vulnerabilities that hackers can exploit to access your photos, messages, location, or payment information. Without the patch, your phone remains exposed to that specific attack until you update. The other changes — new camera features, redesigned settings menus, different notification styles — are visible but less urgent. You notice them when ready. The security fixes you never see, which is exactly the point.
You can see what changed in your specific update by opening Settings, tapping General, then About, and scrolling to the version number. That number tells you which update you have. To see what that update contained, you would search Apple's security updates page for that version number, though the list is technical and long.
Key Takeaways
- Every iPhone update includes security patches that close vulnerabilities hackers can use to steal your data, so installing updates within a week of release protects you from known attacks.
- Major updates (iOS 17 to iOS 18) add visible features and redesign parts of the interface, while minor updates (18.0 to 18.1) mostly contain security fixes and bug corrections.
- You can check which update your phone is running by going to Settings > General > About and looking at the version number.
- Updates install automatically overnight if you plug in your phone and connect to WiFi, so you do not have to remember to do it manually.
How to see what changed in your update
Apple publishes release notes for every update, but they are buried in Settings and written in technical language. The fastest way to see what changed is to open Settings, tap General, then Software Update. At the top of that screen, below the version number, you will see a short description of what that update contains — usually something like "This update includes bug fixes and security improvements."
That description is intentionally vague because most changes are security patches you cannot see. If you want the full technical list, you can visit Apple's security updates page on a computer and search for your iOS version number. The list will show every vulnerability that was patched, but the descriptions assume you understand how code works. For most people, the short description in Settings is enough to know that the update is safe to install.
If you want to know whether a specific feature you use changed, search for that feature name plus "iOS 18" (or whichever version you have). For example, searching "iPhone camera iOS 18 changes" will show you what Apple modified in the camera app. This is faster than reading the full release notes.
When updates arrive and how long they take to install
Apple releases security updates roughly once a month, usually on a Tuesday or Wednesday. Major updates with new features arrive once a year, typically in September. You do not have to install them when ready — security patches remain effective whether you install them the day they arrive or two weeks later. However, the longer you wait, the longer your phone is exposed to the vulnerability that patch fixes.
Installation takes between 15 and 45 minutes depending on the update size and your phone's speed. Your phone will restart during the process, so you cannot use it while updating. The easiest way to update is to plug in your phone, connect to WiFi, and let it update overnight. Go to Settings > General > Software Update, tap read and Install, and your phone will handle the rest once you go to bed.
If you need your phone during the day, you can update manually by going to the same Settings menu and tapping Install Now. Your phone will restart and you will see an Apple logo on a black screen while it installs. Do not unplug it during this time. Once the logo disappears and your home screen returns, the update is complete.
Why some updates are bigger than others
A major update like iOS 18 might be 3 to 5 gigabytes and take 30 to 45 minutes to install. A minor update like iOS 18.1 might be 500 megabytes and take 15 minutes. The difference is what Apple changed. Major updates redesign parts of the interface, add new apps or features, and patch dozens of security holes. Minor updates patch security holes and fix bugs in existing features, but do not add anything new.
You cannot skip a major update and jump to the next one. If you are on iOS 17 and iOS 18 is released, you must install iOS 18 before you can install iOS 18.1. Your phone will not let you skip versions. This is why some people see a very large update waiting — they have skipped several months of updates and now have to install them all at once.
If your phone is running low on storage space, it may not have room to read and install a large update. In that case, you will see a message saying your phone does not have enough space. You can free up space by deleting old photos, videos, or apps, then try updating again. Alternatively, you can connect to a computer running iTunes or Finder and update through that software, which sometimes requires less temporary storage space.
What happens if you do not update
Your phone will continue to work normally if you skip an update. Apps will still open, calls will still ring, and you can still use your phone exactly as before. However, you remain exposed to any security vulnerabilities that the update patched. If a hacker discovers that vulnerability and targets iPhones running your version, they could potentially access your data.
The longer you wait, the more likely that vulnerability becomes public knowledge. Once a vulnerability is widely known, hackers actively exploit it. This is why security researchers recommend installing updates within a week of release — the vulnerability is still relatively unknown, so the risk is lower.
After about two years, Apple stops releasing security updates for older iPhone models. If you are still using an iPhone from 2019 or earlier, you may not receive any more updates. At that point, the security risk grows significantly because vulnerabilities will never be patched. This is one reason people eventually replace older phones.
How to check if your phone is up to date
Open Settings, tap General, then tap Software Update. If your phone is up to date, you will see a message saying "Your software is up to date" with today's date. If an update is available, you will see the version number and a description of what it contains, with a read and Install button below.
If you see a message saying "iOS [version] is recommended" or "iOS [version] is required," that means an update is waiting. Recommended updates are security patches that Apple suggests you install soon. Required updates are critical security fixes that Apple will eventually force you to install before you can use certain features. Neither message means your phone will stop working when ready, but both mean you should update within the next week.
If you have automatic updates turned on, your phone will read and install updates automatically when plugged in and connected to WiFi. To check whether automatic updates are on, go to Settings > General > Software Update > Automatic Updates. If the toggle next to "read iOS Updates" is green, your phone is set to update automatically.
What to do if an update fails or gets stuck
If your phone gets stuck on the Apple logo during an update, or if the update fails and you see an error message, the first step is to force restart your phone. Hold down the volume up button, then quickly release it. Hold down the volume down button, then quickly release it. Then hold down the side button until you see the "slide to power off" screen, release the side button, and slide to power off. Wait 30 seconds, then hold the side button again until the Apple logo appears.
Once your phone restarts, try updating again through Settings > General > Software Update. If the update fails a second time, try connecting your phone to a computer with iTunes (on Windows) or Finder (on Mac), then updating through that software. This method sometimes works when updating directly on the phone does not.
If the update still fails, your phone may have a hardware problem or corrupted storage. At that point, you would need to visit an Apple Store or contact Apple Support. Bring your phone and be prepared to explain what error message you saw and how many times you tried to update.
Frequently Asked Questions
Do I have to update my iPhone right away?
No, but you should update within a week of release. Security patches are most effective when installed promptly, before vulnerabilities become widely known. If you wait months, you remain exposed to attacks that could have been prevented. However, updating a few days late is not urgent — the risk is still low.
Will the update delete my photos or messages?
No. Updates preserve all your data, photos, messages, and settings. Your phone will restart during the update, but everything on it remains exactly as it was. The only exception is if the update fails and you have to erase your phone to fix it, which is extremely rare.
Can I use my phone while it is updating?
No. Your phone will restart and display the Apple logo while the update installs. You cannot make calls, send messages, or use any apps during this time. This is why updating overnight is convenient — your phone updates while you sleep and is ready to use in the morning.
What if I do not have WiFi when an update is available?
You can update over cellular data, though it will use a significant amount of data — usually between 500 megabytes and 5 gigabytes depending on the update size. If you have a limited data plan, wait until you are on WiFi. Your phone will not force you to update when ready, so you can wait a few days until you are somewhere with WiFi.
Why does my phone say an update is required?
Required updates are critical security patches that Apple considers essential. Your phone will continue to work, but Apple may eventually restrict certain features until you update. This is rare and usually only happens for very serious vulnerabilities. Install the update as soon as you can, but you are not locked out of your phone when ready.