Is Outlook running slowly, showing outdated messages, or refusing to sync? Learning how to clear Outlook cache files is often the fastest fix. Bloated or corrupted cache data sits behind a surprising number of Outlook problems, from broken search to stuck send and receive loops, and clearing it forces Outlook to rebuild fresh temporary files from your mailbox.
This guide covers every version of Outlook: the classic desktop app, the new Outlook for Windows, Outlook on the web, and the Outlook mobile apps for iOS and Android. For each platform you will find clear steps, warnings about what is safe to delete, and guidance on which cache to target for each symptom, so you fix exactly what is broken and leave everything else alone.
What the Outlook Cache Does (and When It Causes Problems)
Outlook keeps several layers of cached data so it can work quickly, and even function while you are offline. The desktop app stores a local copy of your mailbox in an offline data file, keeps copies of forms, views, and customisation data in a folder called RoamCache, and remembers every address you have ever typed in the autocomplete or “nickname” cache. Outlook on the web relies on your browser cache instead, while the mobile apps keep their own temporary data on your phone.
This caching is normally invisible and helpful. Problems start when any of these files grow too large or become corrupted. Typical symptoms include search results that miss recent emails, folders that show old message counts, autocomplete suggestions for people who left the company years ago, calendar entries that refuse to update, and the frustrating situation where Outlook insists you have new mail that does not exist.
Clearing the cache is a low-risk first step because these are all disposable copies. Your actual emails, contacts, and calendar items live on the mail server or in your mailbox data file, and Outlook simply rebuilds the cache from that source, which is exactly what happens when you clear Outlook cache files the right way.
How to Clear Outlook Cache on Desktop (Classic and New Outlook)
Before you clear Outlook cache data in the desktop app, close Outlook completely. Check the system tray near the clock, because Outlook often keeps running in the background after you close the main window. Right-click its icon and choose Close or Exit so no files are locked while you work. Each method below targets a different way to clear Outlook cache components, so start with the one that matches your symptom.
Clear the Autocomplete (Nickname) Cache
The autocomplete cache is the list of suggested addresses that appears when you start typing in the To field. Old or incorrect entries here can cause emails to bounce to dead addresses, so it is worth pruning now and then.
- In classic Outlook, go to File > Options > Mail.
- Scroll to the Send messages section and click Empty Auto-Complete List.
- Confirm the deletion. Outlook will rebuild the list from addresses you use going forward.
To remove a single bad suggestion instead of wiping the whole list, start typing the address in a new email, hover over the unwanted suggestion, and click the X (or press Delete with it highlighted).
Delete the RoamCache Files
The RoamCache folder holds cached forms, views, and other customisation data. When Outlook misbehaves after an update or shows garbled message views, deleting these files often helps.
- Make sure Outlook is fully closed, including the system tray icon.
- Press Windows key + R, type %localappdata%\Microsoft\Outlook\RoamCache, and press Enter.
- Select all files in the folder (Ctrl + A) and delete them.
- Restart Outlook. It will recreate the files it needs automatically.
Warning: delete only the contents of RoamCache, not the folder itself, and do not touch neighbouring folders such as the one containing your OST data file. When you clear Outlook cache folders like RoamCache, custom views and forms reset to defaults, so take a screenshot of any heavily customised view first.
Clean Up Temporary Files and Compact the Data File
Classic Outlook also accumulates temporary files that you can sweep away with the built-in mailbox cleanup tools. Go to File > Tools > Mailbox Cleanup to find old items, empty the Deleted Items folder, and see the size of each folder. Large mailboxes slow everything down, so archiving or deleting old mail is often more effective than any cache trick.
If Outlook feels sluggish despite a tidy mailbox, compacting the offline data file can help. Go to File > Account Settings > Account Settings > Data Files, select your data file, click Settings, then Compact Now. For the new Outlook for Windows, most cache management happens automatically, but signing out and back in under Settings > Accounts refreshes its locally stored data.
If messages still refuse to update after a cleanup, the problem may run deeper than the cache. In that case, work through our guide to fix Outlook sync issues for the full checklist, from recreating the mail profile to repairing the data file.
How to Clear Outlook Cache in Outlook on the Web
Outlook on the web (outlook.office.com) stores its cache inside your browser, so the fix is to clear the browser data for the Outlook site. The exact steps depend on your browser, but the principle is the same everywhere.
In Google Chrome or Microsoft Edge:
- Open Outlook on the web and press Ctrl + Shift + Delete to open the clear browsing data dialogue.
- Set the time range to All time.
- Tick Cached images and files (and cookies if you are happy to sign in again).
- Click Clear data, then reload the Outlook tab.
In Firefox: press Ctrl + Shift + Delete, choose Everything from the time range, tick Cache, and click Clear Now. Whichever browser you use, the aim is the same: clear Outlook cache entries tied to the Outlook site so the app loads a clean copy of its interface.
If you want to clear Outlook cache data without touching your other websites, most browsers let you delete data for a single site. In Chrome or Edge, go to Settings > Privacy and security > Cookies and site data > See all site data, search for office.com or outlook.live.com, and remove just those entries. You will need to sign in to Outlook again afterwards, so keep your password handy.
How to Clear Outlook Cache on Mobile (iOS and Android)
The mobile apps behave differently on each platform, so follow the instructions for your phone.
iPhone and iPad
iOS does not let you clear Outlook cache storage directly from inside the app. Instead, you have two options. The gentler one is to offload the app: go to Settings > General > iPhone Storage > Outlook and tap Offload App. This removes the app itself but keeps your accounts and documents, then reinstalls a fresh copy when you tap the icon again.
If offloading does not help, delete the app entirely and reinstall it from the App Store. You will need to add your email accounts again afterwards, so make sure you know your passwords before you start.
Android
Android gives you a proper cache-clearing option:
- Open Settings > Apps > Outlook (on some phones it is Apps > See all apps > Outlook).
- Tap Storage & cache.
- Tap Clear cache. Do not tap Clear storage unless you are prepared to set up your accounts again, because that wipes all app data.
- Reopen Outlook and check whether the problem is gone. This simple clear Outlook cache routine resolves most mobile refresh problems without touching your accounts.
Outlook Cache Types: Where They Live and When to Clear Them
The table below summarises every method in this guide so you can pick the right clear Outlook cache approach for your symptom instead of deleting things at random.
| Cache type | Where it lives | Clear it when… |
|---|---|---|
| Autocomplete / nickname cache | Your Outlook profile (desktop app) | Old or wrong addresses keep appearing as suggestions |
| RoamCache (forms, views, customisations) | %localappdata%\Microsoft\Outlook\RoamCache | Message views look broken, forms misbehave, or problems started after an update |
| Offline data file (OST) | %localappdata%\Microsoft\Outlook | Folders will not sync or the file has grown enormous (recreate it via a new mail profile rather than deleting it by hand) |
| Browser cache | Your web browser | Outlook on the web shows stale data, will not load, or throws script errors |
| Mobile app cache | iOS or Android app storage | The mobile app crashes, shows outdated mail, or will not refresh |
| Temporary files and mailbox clutter | Deleted Items and oversized folders | Outlook is slow overall even though the caches themselves are healthy |
What Clearing the Cache Will Not Fix
Clearing the cache is a remedy for corrupted or stale temporary data, not a cure-all. If you clear Outlook cache files and the problem persists, the cause probably lies elsewhere. Here are the most common situations where a different fix is needed:
- Authentication failures. Repeated password prompts usually mean an expired password, a revoked app password, or a multi-factor authentication hiccup, not a cache problem.
- Specific error codes. Codes such as pii_email faults point to installation or profile corruption rather than stale cache data. Work through our guide to fix Outlook pii_email errors instead of clearing caches repeatedly.
- Send and receive errors. Messages stuck in the Outbox or 0x800-series errors often involve account settings, ports, or antivirus interference. Our Outlook send and receive error fix walkthrough covers those step by step.
- Server-side issues. If Outlook on the web and your phone both fail at the same time, the problem is almost certainly with the mail server or your account, and no amount of local cache clearing will help.
- Sync problems that survive a cache clear. When folders still refuse to update, the deeper checklist in our guide to fix Outlook sync issues — recreating the mail profile, checking filters, repairing the data file — is the next step.
How Often Should You Clear the Cache in Outlook?
Most people never need to clear Outlook cache data on a schedule. Outlook manages its caches well under normal conditions, and routine clearing just forces the app to re-download data, which costs time and bandwidth for no benefit.
Treat cache clearing as a troubleshooting step, not maintenance. A sensible rule of thumb: clear Outlook cache files only when a specific symptom points at the cache, never on a calendar schedule. The one exception is the autocomplete cache, which is worth pruning once or twice a year so dead addresses stop cluttering your suggestions.
If you find yourself clearing the same cache every few weeks, something deeper is wrong — a corrupted mail profile, a failing drive, or an add-in that keeps breaking things. Fix the root cause instead of repeating the workaround.
Frequently Asked Questions
Will I lose emails if I clear Outlook cache?
No. Cache files are disposable copies; your emails live on the mail server or in your mailbox data file. When you clear Outlook cache files, Outlook simply downloads fresh copies. The one exception is the autocomplete list, which is genuinely deleted — but it rebuilds itself as you send mail.
How long does Outlook take to rebuild its cache?
It depends on your mailbox size and connection speed. A small mailbox may finish in minutes, while a 20 GB mailbox on a slow connection can take hours. Leave Outlook open and connected until the status bar shows “All folders are up to date”.
Why is Outlook still slow after I cleared the cache?
A fresh cache cannot fix a bloated mailbox, a corrupted mail profile, or a misbehaving add-in. Try compacting the data file, disabling add-ins under File > Options > Add-ins, and archiving old mail. If nothing helps, creating a brand-new mail profile is the next logical step.
Does clearing the cache sign me out of Outlook?
On the desktop app, no — your accounts stay configured. In Outlook on the web, clearing cookies (not just cached images) will sign you out, so keep your password ready. On mobile, “Clear cache” keeps you signed in on Android, while deleting and reinstalling the app on iOS means adding your accounts again.
Is it safe to delete everything in the Outlook AppData folder?
No. Only delete the contents of the RoamCache folder, or use Outlook’s built-in cleanup tools. Deleting your OST data file or profile folders by hand can break your mail profile. If the OST itself is corrupt, recreate it through a new mail profile in Control Panel > Mail rather than deleting files manually.
Can I clear the Outlook cache with a single button?
There is no universal button, because each platform stores its cache in a different place. That is why this guide covers desktop, web, and mobile separately — pick the section that matches where you actually use Outlook.