How to Fix “Source file could not be read” Error on Firefox?

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Just like Google Chrome, Safari, and Internet Explorer, Firefox is also considered a powerful browser in the industry. Although lacking in the numbers when compared to the earlier mentioned browsers, it does boast significant and handy features. However, this does not mean the minority that appreciates and remains loyal to Firefox are free from bugs and errors.

This article addresses the issue that leads to a “source file could not be read” error message on Firefox.

What Is the “Source file could not be read” Error on Firefox?

When users attempt to download a file from the internet using Mozilla Firefox, they might encounter a “Source file could not be read” error message. This issue can occur while downloading any sort of file, from games to documents, music, or videos. The error message completely hinders the download of the file with the browser displaying the following message:

“could not be saved, because the source file could not be read. Try again later, or contact the server administrator.”

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Although this error is common among Firefox users, there are instances where it has been recorded in other platforms such as Google Chrome and Edge. The message displayed doesn’t give a conclusive solution and trying the download the alternative browsers will only bear the same results.

What Causes the “Source file could not be read” Error on Firefox?

The common cause related to the “Source file could not be read” error is the loss of internet connection. So, if you encounter this error on Firefox, you must first check if your internet connection is good. If that doesn’t help, you may proceed with the solutions presented below.

The “Source file could not be read” error may also occur due to corrupt system files. These are files that an average user barely has access to. These files can be damaged, corrupted, or missing if tampered with by an inexperienced user.

However, the major culprit to damaging or corrupting system files is a virus program. Malicious apps tend to access sacred places of the computer just to mess with some of the vital system files. This will then weaken the computer’s security measures, allowing more malware to infiltrate the system.

So, if you encounter a “Source file could not be read” error on Firefox, you must not rule out the possibility of a virus infection. We advise conducting a full system security scan using strong anti-malware software to fix the issue.

The other cause of this issue can be a rogue extension that may be clashing with the Firefox browser. A corrupt storage drive can be another cause with the browser failing to find a suitable place to keep the data of the file waiting to be downloaded.

Another culprit can be your VPN. Some VPN services can configure your system settings to prevent downloading large files in an attempt to limit data usage.

Ways to Fix the Firefox Error “Source file could not be read”

As already mentioned, the “Source file could not be read” error can be mild to severe depending on the cause of the issue. Regardless of what’s causing the error to appear, we have prepared several solutions that you can try out. If you are not sure of the cause, we advise applying these solutions in a chronological manner for better results.

Solution #1: Fix the Internet Connection

This is the initial, less time consuming, and easiest solution on the list. You can check on your other devices connected to the same network if the internet connection is good. Moreover, you must also check if your ISP is not blocking the download of the file.

  1. Press Windows + I keys to launch the Settings app.
  2. Now, click Network & Internet.
  3. Select Network troubleshooter and the diagnosis window will launch with processes beginning to check for any connection problems.
  4. If found, a recommended solution will be offered. Select it to apply the fix.

If no issues were found during the diagnosis, you may proceed to the next solution.

Solution #2: Erase Damaged Compreg.dat File

Corrupt files are a common cause of numerous errors. In this scenario, a corrupt Compeg.dat file can be the cause of the “Source file could not be read” error. To fix the issue, you must delete the file. Here’s how:

  1. Access the Firefox browser and type about:support into the text field before hitting the Enter key.
  2. Click the Open Folder or Show Folder to access the Firefox profile.
  3. Close the browser, and then right-click on the Compreg.dat file from the profile folder. Click Delete.
  4. When done, restart the computer and check if the issue has been resolved.

Solution #3: Get Rid or Deactivate Firefox Extensions

As indicated earlier on, rogue extensions can be the cause of the “Source file could not be read” error. At times, an extension could be incompatible with Firefox. Regardless, the best solution is to get rid of the suspicious extensions.

  1. Access Firefox, and then go to the menu.
  2. Click Add-ons before selecting Extension.
  3. Click the Disable option next to the suspicious extension.
  4. If you are sure of the culprit, you can click the Remove button to delete the extension permanently.

Solution #4: Verify if Places.sqlite Attributes Are Not Configured to Read-only

If the Places.sqlite attributes are set to read-only, then it might be the cause of the issue. Therefore, you must check and configure the settings properly.

  1. Open the Firefox browser and type about:support into the address bar before hitting the Enter key.
  2. Now, select the Open Folder option, and then access the Firefox profiles folder from File Explorer.
  3. From the emerging folder, locate places.sqlite, and then right-click before selecting Properties.
  4. From the window that appeared, uncheck the box next to the Read-only option under the Attributes section.
  5. Click Apply before selecting the Ok button to save the changes.

Solution #5: Reinstall the Firefox Browser Application

Corrupt or damaged browser application files can trigger the “Source file could not be read” error. But you can solve the issue by reinstalling the browser. This will refresh the files, replacing damaged ones with fresh copies. Doing so will also get rid of the issue that caused the error.

  1. Press the Windows key, and then type Control Panel before hitting the Enter key.
  2. Now, click the Programs and Features option.
  3. Go through the installed programs and find Mozilla Firefox.
  4. Right-click on it, and then select Uninstall from the emerging menu.
  5. Follow the prompts to complete the uninstallation process.
  6. When done, restart the system, and then access the official Firefox site to download the application and install it.


There is one thing common about apps and PC errors, and that is the possibility of being infected by a virus. Therefore, we advise investing in a strong and reliable anti-malware to keep your system free from viruses. Moreover, trusted security programs can fight malware attacks in the background in real-time while you surf the internet productively.

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