Starting back in September of 2018, the ESO Launcher has been hanging for some users every time it tries to update.

UPDATE: On 3/28/19 a new version of the Launcher was published and a few days later once it had rolled out to users, pretty much everyone who previously had this problem has reported the launcher FINALLY patches correctly again. I'm leaving this guide in place in case the problem starts up again.


The symptoms of this problem are:

• the launcher will freeze/go unresponsive while downloading (typically at less than 10% complete),
  
• consume large amounts of CPU (25-40%), and
  
• continually write error messages to its own log file (host.developer.log) until the log file grows so large (100s of GB) that the launcher crashes completely.

If you're seeing these symptoms, this guide is for you. There is a long thread on the ESO forums[forums.elderscrollsonline.com] about the issue, but Zenimax have given up on trying to fix it (or even replying to the thread).

The crux of the problem is that the launcher is trying to download patch files from the Akamai content delivery network and is failing for some users. The launcher doesn't know how to deal with those failures and crashes.

Most ISPs have servers within their own networks that mirror Akamai content files. The launcher attempts to use one of these ISP-hosted servers in preference to the master update server because it saves Zenimax money on bandwidth fees. The problem is that for some reason, the launcher corrupts the patch files[forums.elderscrollsonline.com] when downloading from some (but not all) servers, depending on your region and ISP. Its internal error handling code is incapable of dealing with this corruption properly, so it goes into an infinite loop of logging errors to its log file.

Zenimax have publicly stated that this is an ISP issue[forums.elderscrollsonline.com] and that certain ISPs are blocking the files, and are no longer investigating the problem. This problem with that explanation is that the log shows the exact URL that is failing and you can copy and paste that URL into Chrome and get it to download correctly, which is pretty solid proof that your ISP is not blocking it at all. The launcher itself is not actually developed by Zenimax, but is outsourced to Solid State Networks[www.solidstatenetworks.com], which probably explains why Zenimax appear to have no clue what the problem is.

Workarounds successfully used by some users are as follows:

1. Using a VPN while patching. This generally works because you end up bypassing the problematic ISP-hosted update server by virtue of not downloading through your regular ISP. However, this can mean paying extra money if you need to download more than the free tier allows on whatever VPN you select. It can also be a lot slower than it would be if the launcher was working correctly.
   
   
2. Downloading the patch files using a web browser. By picking through the log files it is possible to find out which files are needed, download them manually using Chrome, and place them in the correct location for the launcher to apply them. This works but is more complicated and gets real tedious when patches are coming out on a weekly basis. I did it for a few weeks before I got bored and went looking for a better solution.

After getting bored with the second method above, it occurred to me that as bad as the launcher is at dealing with download corruption, it might be able to handle not being able to contact its preferred update server. This hunch proved correct. By blocking access to the local CDN server that it tries to use by default, we can force the launcher to source its update files elsewhere, which results in a successful download.

• You need to know where the launcher is installed on your hard disk so you can find both the .exe and its log file.
  
  If you installed Steam and ESO in the default Windows location, it will be at C:\Program Files (x86)\Steam\steamapps\common\Zenimax Online\Launcher
  
  
• You need to know what the IP address of your ISP's awful CDN mirror is.
  
  When the launcher crashes, it's because it is writing the server location that is failing to its log file a million times. Open the host.developer.log in the above folder and you'll see it listed over and over as soon as you are past the first couple hundred lines in the log. An example is below. Notepad may hang when you try to open the log file due to the size. Try Notepad++[notepad-plus-plus.org] instead.
  
  The IP address is right after the http:// (bolded and underlined below for emphasis)
  
  http://151.205.4.95:80/data/046f7c60b3945d28/live.patcher.elderscrollsonline.com/products/eso/874DCDCF-C40C-4956-92FE-E39B8DC4764E/depot/depot_273to275/depot_273to275.z01
  
  This IP will probably be different for you so DO NOT just use the one I found in my log (151.205.4.95). You must use the IP address from your own log in the steps below (specifically step 7).
  
  NOTE: In some cases, the launcher may try a second, different IP address from the CDN after you block the first one. If the launcher still hangs after following the below steps, you may need to check the log again to see if there is a different IP address listed with the same error message as the first, and then block that one too.

Now that you have those two pieces of information, we're going to cut the ESO launcher off from this IP address forever.

Run the following command from an elevated command prompt, substituting in the correct values for the location of the launcher and the IP address it is trying to download from:


The command should be all on 1 single line (it should already be that way if you copy it from the box above unless your browser is doing something weird).

Remember, if you just copy & paste this command without making sure the launcher path and IP address are correct for your system, the above command will not fix your problem. Make sure the program= and remoteip= values are correct!

OK, bear with me because there are a few steps here and it may well be stuff you're not familiar with, but I've included step-by-step screenshots and and you should only have to do it once (hopefully).

1. Go to the Start Menu and type firewall with. This should bring up a search result for Windows Defender Firewall with Advanced Security. Click it.
   
   
   
   
2. You may never have seen this program before, but's it's about to become your BFF. Right-click on Outbound Rules and click New Rule...
   
   
   
   
3. Click Custom, then Next
   
   
   
   
4. Click This program path then Browse to locate your Bethesda.net_Launcher.exe (it's in the location from step 1. Mine looks different because I have my ESO install on a second HD.)
   
   
   
   
5. Just click Next on the Protocols and Ports page.
   
   
   
   
6. In the second half of the Scope page, select These IP addresses and then click Add...
   
   
   
   
7. Copy & paste the IP address from your log file (NOT THE ONE FROM THIS EXAMPLE unless they really are the same) and click OK.
   
   
   
   
8. Once you are back on the Scope page, click Next, then make sure Block the connection is selected on the Action page and click Next again.
   
   
   
   
9. Just click Next on the Profile page.
   
   
   
   
10. Lastly, give your firewall rule a friendly name and click Finish
    
    
    
    
11. Delete the host.developer.log from the folder in step 1. When it's too big, it will crash the launcher even if there are no download errors
    
    
12. Load the launcher, and enjoy your patching.