Thunderbird

How to Delete or Clear Cache in Thunderbird? 6 Easy Methods

By Admin

Updated: March 19, 2026 ~ 4 Minutes Reading

Table of Contents

Users want to clear the cache in Thunderbird whenever Thunderbird is not working properly, causing sync errors or starting to cause file corruptions.

Here we have 6 ways to delete UI, IMAP, and other disk cache in Thunderbird.

How Cache & Cookies Work in Thunderbird?

With an email client like Thunderbird, a lot of data is stored locally temporarily, like email headers, partial email content (mostly for opened emails), attachments, etc.

This enables you to view them offline and make your email management experience better and faster.

Note: For IMAP accounts, the complete data is stored on the remote server and synced as needed. Temporary cache enables local viewing when offline. For POP accounts, complete data is stored locally on your Thunderbird profile on the desktop.

You need to clear the cache in Mozilla Thunderbird frequently, and cache files are more vulnerable to corruption, which may further lead to email data loss.

Use a professional Thunderbird Backup Tool to back up all data in the Thunderbird profile to avoid data loss in such situations.

Does Thunderbird Use Cookies?

No, Thunderbird does not store cookies like web browsers for personalisation, tracking, and analysis to study user behaviour. It is a free and open source platform.

Safely Clear Cache in Thunderbird – Step-by-Step Guide

The method given below is to empty Thunderbird cache on all Mac and Windows devices and can be easily followed along on all the latest Thunderbird versions.

Method 1: Clear Disk Cache in Thunderbird

  1. On your computer, open Thunderbird.
  2. Click on Menu on the top-right.
  3. Go to Settings >> General.
  4. Scroll to the Disk Space section.
  5. You will see how much data is stored in cache.
  6. Press Clear Now to delete Thunderbird cache.
    Clear Disk Cache in Thunderbird

There are multiple other ways to empty out the system cache in Thunderbird, given below:

Method 2: Empty Startup Cache in Mozilla Thunderbird

  1. Open Thunderbird Navigational Menu.
  2. Select Help >> Troubleshooting Information.
  3. Click on the Clear Startup Cache option.
    Empty Startup Cache in Mozilla Thunderbird
  4. Select the Restart Thunderbird option.

Method 3: Delete IMAP Cache Entries

MSF or Mail Summary File stores data like email headers, time stamps, folder structure, etc.

You can rebuild Thunderbird Index to delete IMAP-related cache.

Ensure restarting to rebuild them without older or corrupted cache data.

Method 4: Delete Cache Folders from Thunderbird Profile

  1. Open Thunderbird on your desktop.
  2. Go to Menu >> Troubleshooting Information.
  3. Scroll to the Profile Folder and press Open Folder.
  4. Look for a shader-cache folder, or in an earlier version, also known as the cache2 folder.
    delete shader-cache folder in Thunderbird
  5. Close Thunderbird app.
  6. Right-click and delete the folder, and then restart Thunderbird.

Method 5: Clear Thunderbird Associated Temp Files

Your system also stores some additional and unnecessary Mozilla or Thunderbird-related temporary files. Follow the steps to clear the cache in Thunderbird for Windows or macOS:

  1. Press Win+R or Command+Space.
  2. Type in %TEMP%.
  3. Search for Mozilla or Thunderbird.
  4. Right-click on the files and delete the cache.
    Thunderbird Associated Temp Files

Method 6: Compact Thunderbird Folders

Note: Compacting the folder is not a method to clear out Thunderbird cache. However, deleting them gets rid of older deleted Thunderbird emails still stored in the profile folder on your PC.
  1. Open Thunderbird.
  2. Right-click on each Mailbox one by one.
  3. Choose the Compact Folder option.

Advantages of Clearing Thunderbird Cache

Learn More: How to Restore Thunderbird Backup?

FAQs: Empty Cache Thunderbird

Q1: Where is the Thunderbird cache?
Thunderbird cache folders are stored in Thunderbird profiles separately by the shader-cache or cache2 folder name.

Q2: How do I clear storage in Thunderbird?
Thunderbird mailbox is full, try solutions like compacting the folder, clearing the cache, emptying out the trash, and spam folder.

Q3: Will I lose my emails if I clear the cache in Thunderbird?
No, the cache folder does not store emails, but only stores temporary data. Your emails are safely stored on your IMAP server and dedicated MBOX field in the profile folder for PO accounts.

Q4: Is there a specific Thunderbird add-on to empty the cache?
Clear IMAP Local Cache is a well-known add-on to delete Thunderbird cache. However, the manual methods mentioned above will help better remove the cache.