You know that feeling. You go to download a new app or snap a quick photo of something hilarious, and that dreaded "Storage Almost Full" notification pops up. You check your settings, expecting to see a bloated photo library or maybe too many podcasts. Instead, you find a massive, grey bar labeled "System Data" or "Other." It’s taking up 20GB. Maybe 40GB. It feels like a ghost in the machine. Honestly, it’s one of the most frustrating parts of modern smartphone ownership because the OS doesn't exactly give you a "delete" button for it.
System Data is a catch-all junk drawer. It’s where your phone stashes caches, logs, Siri voices, localized languages, and partially downloaded updates. It’s the digital equivalent of that one kitchen drawer filled with dead batteries, mystery keys, and soy sauce packets. If you want to how to reduce system data, you have to stop looking for a single switch and start cleaning out the corners.
What is System Data anyway?
On an iPhone, Apple defines System Data as things that don't fall into the standard categories like Apps, Photos, or Media. This includes the Safari cache, Mail attachments, and even the system’s own indexing databases. On Android, it's often similar—miscellaneous files that the OS needs to run quickly but doesn't necessarily need to keep forever.
The tricky part? System Data is dynamic. It grows and shrinks. If you’re streaming a lot of 4K video on Netflix or scrolling through endless high-res reels on Instagram, your phone is "caching" that data so it doesn't have to redownload it if you watch it again. That cache is parked in System Data. If you don't have much free space, the OS is supposed to prune this automatically. But it’s not always great at it. Sometimes it just sits there, hoarding space like a digital packrat.
The Safari and Chrome problem
Your web browser is likely the biggest offender. Every single website you visit stores a little bit of data on your phone. Think of it as a "save state" for the internet. If you haven't cleared your history in months, you’re likely sitting on several gigabytes of purely useless "System Data."
For iPhone users, head into Settings, find Safari, and look for "Clear History and Website Data." It feels aggressive to wipe it all, but it’s a massive win for your storage. Android users can do the same within Chrome settings under "Privacy and Security." You’ll be surprised. I’ve seen phones regain 5GB just from this one step.
Streaming apps are lying to you
You might think that because you aren't "downloading" movies, they aren't taking up space. Wrong. Apps like TikTok, YouTube, and Spotify are notorious for filling up System Data. They "buffer" content ahead of time.
Take TikTok. It’s essentially a cache machine. As you swipe, it’s downloading the next three videos in the background. If you spend two hours on the app, that’s a lot of data being temporarily stored. While the app itself might only be 300MB, its "Documents and Data" (which feeds into System Data) can easily balloon to several gigs.
One weirdly effective trick for how to reduce system data involves offloading these apps. On iOS, "Offloading" deletes the app but keeps your personal data and login info. When you reinstall it, the bloat is gone, but your account is still there. It’s a surgical strike against cache.
The Message attachment graveyard
We all have that one group chat. You know the one. It’s been active since 2019. Thousands of memes, "good morning" GIFs, and short videos have been sent there. Even if you don't "save" these to your camera roll, your phone keeps them in the background so you can scroll back through the conversation.
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This is a huge part of System Data. In iOS, you can go to Settings > General > iPhone Storage > Messages. It will show you "Large Attachments." Deleting these is cathartic. You don't need that grainy video of your cousin’s wedding from three years ago taking up 150MB of precious flash storage.
The Nuclear Option: Why a backup and restore actually works
Sometimes, System Data gets "stuck." This usually happens after a major OS update—like moving from iOS 17 to iOS 18. Bits of the old operating system or broken update logs get lodged in the storage, and the phone doesn't know how to delete them.
If you've tried everything and that grey bar is still massive, it’s time for the "Nuclear Option."
- Back up your phone to iCloud or a computer (encrypted backups are better because they save passwords).
- Factory reset the device. Wipe it clean.
- Restore from that backup.
It sounds like a massive pain. It is. But it works. When you restore from a backup, the phone only pulls back the essential "stuff"—your apps, your photos, your settings. It leaves behind the corrupted logs and useless caches that were bloating the System Data. It’s like moving into a new house and realizing you didn't actually need all that junk in the attic.
Smart maintenance for the long haul
You shouldn't have to factory reset your phone every six months. That’s insane. Instead, change how the phone handles data automatically.
On iPhone, go to Settings > Messages > Keep Messages. Change it from "Forever" to "1 Year" or even "30 Days" if you’re a minimalist. This prevents the attachment graveyard from ever returning.
Also, keep an eye on your "Recently Deleted" folder in Photos. Photos you delete stay on your device for 30 days. They count toward your storage until they are truly gone. Emptying that folder is an instant win.
Does "System Data" ever actually go to zero?
No. And you don't want it to. Your phone needs some system data to function. It needs the local database that tells it where your files are. It needs the fonts you use. It needs the specialized Siri voice that sounds like a real person instead of a robot from a 1980s sci-fi movie. A healthy amount is usually between 5GB and 10GB. If you’re under that, stop worrying. If you’re over 20GB, something is definitely wrong.
Real-world insights on Android
Android handles things slightly differently. Use the "Files by Google" app. It’s surprisingly good at identifying "junk files." Unlike the built-in settings menu, it can sniff out duplicate files and old (.apk) installers that you don't need anymore. Android users also deal with "System" and "Other" separately. Usually, "System" is the actual OS, which you can't touch. "Other" or "Cached Data" is what you’re hunting.
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Actionable steps to clear the bloat right now
Stop reading and do these three things immediately. First, clear your browser cache. It’s the easiest win. Second, go to your most-used social media app (TikTok, Instagram, or X) and look for a "Clear Cache" option within the app's own settings. Third, check for a pending software update. Sometimes System Data spikes because the phone has downloaded an update but hasn't installed it yet. Installing the update often flushes the temporary files used during the process.
If you’re still struggling, look at your "Books" or "Podcasts" apps. Downloaded audiobooks and 2-hour podcast episodes are massive. Most people forget they’ve downloaded a dozen episodes they’ll never actually listen to. Switch your podcast app to "Remove Played Downloads" to keep the storage from creeping back up.
Managing storage is a game of inches. You don't find one 10GB file to delete; you find twenty 500MB files. It’s tedious, but your phone will run faster, and you’ll finally be able to take that photo when it actually matters.