Chrome is one of the best and most popular browsers worldwide for various reasons. The Google ap­plic­a­tion does not only have the repu­ta­tion of being es­pe­cially fast, but also very secure. If you create an account, you can use automatic syn­chron­isa­tion from any device to access all settings at the same time, set favorites, and even access open tabs. In addition, design templates, apps, and ex­ten­sions can be used to tailor the look and func­tion­al­ity perfectly to your own needs – re­gard­less of whether a Windows, Linux, or macOS operating system is used.

But even Google's miracle weapon – like any other software – is not com­pletely problem and error free. More fre­quently seen error messages include the error code ‘ERR_SSL_PROTOCOL_ERROR’, which informs the browser user that there was a failed secure con­nec­tion to the contacted server. What exactly is this SSL con­nec­tion error and how can the ERR_SSL_PROTOCOL_ERROR be fixed?

What lies behind the SSL con­nec­tion error?

The times when the web was simply used as an in­form­a­tion platform are a thing of the past. Today, PC and mobile device browsers are being used more fre­quently to make money transfers, play games, buy products, store files in the cloud, or interact with other users. The fact that more and more personal and sensitive in­form­a­tion is being trans­ferred means that it’s becoming easier for criminals. Customer data, company internals, and other private data are es­pe­cially favoured by thieves nowadays, which is why SSL and TLS have become an absolute must. The security protocol, which is based on the standard Web protocol HTTP, guar­an­tees secure con­nec­tions via cer­ti­fic­ate exchange. It also ensures that the data streams are trans­mit­ted in encrypted form. If an SSL-protected website is accessed with the Google browser and the secure con­nec­tion does not work, the ‘ERR_SSL_PROTOCOL_ERROR’ message will appear. This is how Chrome informs the user that there is a problem pre­vent­ing the necessary cer­ti­fic­ate exchange.

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Possible causes for ERR_SSL_PROTOCOL_ERROR

If Chrome displays the error message when calling up an HTTPS address, the browser provides the following, very general ex­plan­a­tion for why the con­nec­tion setup has failed:

‘Unable to make a secure con­nec­tion to the server. This may be a problem with the server, or it may be requiring a client au­then­tic­a­tion cer­ti­fic­ate that you don't have.’

Much of the in­form­a­tion cannot be inferred from this de­scrip­tion, as it simply states that the problem exists either on the server side or on the client side (browser side). The former is often due to the fact that the contacted site is SSL/TLS certified, but the cer­ti­fic­ate hasn’t been renewed in time and has expired. In addition, a wide variety of technical problems can also be re­spons­ible for the exchange of cer­ti­fic­ates not working.

Note

If you suspect a server error is behind an ERR_SSL_PROTOCOL_ERROR message, it may make sense to come back to the website later. If the problem persists, you should contact the re­spons­ible webmaster.

If the ERR_SSL_PROTOCOL_ERROR has to do with the user's browser, this can be due to many reasons. Contrary to what appears to be the case in the above de­scrip­tion, it is quite possible that the client has the au­then­tic­a­tion cer­ti­fic­ate and the server simply cannot find it. The most common, well-known reasons include the following:

  • the system date or time is not correct
  • the website or IP address is blocked by a firewall or an antivirus program
  • SSL/TLS con­nec­tions are blocked by a firewall or antivirus program
  • the HOSTS file is corrupted
  • the SSL or browser cache contains outdated cer­ti­fic­ate versions
  • Chrome ex­ten­sions are causing the error message
  • QUIC protocol is blocking the con­nec­tion setup

Fixing the ERR_SSL_PROTOCOL_ERROR – how it works

The list of possible causes for the ERR_SSL_PROTOCOL_ERROR message shows that there is no general solution. Instead, there are several options that you can try to solve the SSL con­nec­tion problem on your own. First of all, you can try a "trick", which always proves to be an effective means of dealing with various web errors: re­start­ing your router. It is not uncommon for con­nec­tion problems to disappear when the device re­con­nects to the Internet. If the message still appears in the Chrome browser, you can try these solutions:

Solution 1: check the system date/time

Since incorrect system dates and times can cause the SSL/TLS con­nec­tion to fail, you should take a look at the system clock when the ‘ERR_SSL_PROTOCOL_ERROR’ message appears in your Chrome browser window. If there is a sig­ni­fic­ant dif­fer­ence between what’s shown and the actual time or if the wrong date has been set, the browser is often unable to load SSL con­nec­tions correctly. Make sure that the date and time are correct and adjust them if necessary. By default, you can do this directly from the taskbar – al­tern­at­ively, you can find the right menu under ‘Date and time’ in the Control Panel.

Image: Windows system preferences: date and time
By default, operating systems set the correct time values when the device is connected to the Internet – and also take the time change into account.

Solution 2: tem­por­ar­ily disable antivirus and firewall programs

Software (to protect against malware) and a firewall are mandatory for every user who plans to connect their device to the Internet. However, since security tools like these work with various al­gorithms and rules, they can prevent access to certain websites even if they don’t pose a security risk. For example, it is possible that the IP address or domain address has been clas­si­fied as a security risk and that’s why it’s being blocked. Chrome also displays the ERR_SSL_PROTOCOL_ERROR message if SSL con­nec­tions are generally blocked by a tool.

You can easily test whether the security programs you are using are trig­ger­ing the error message by tem­por­ar­ily disabling them and re­vis­it­ing the website in question. If the con­nec­tion setup now works without problems, you know that you have to make changes in the settings of the programs and remove the IP address from the blacklist.

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Solution 3: delete SSL cache and browser cache

In some cases, cached in­form­a­tion in the SSL cache (SSL status) or browser cache may also be re­spons­ible for the ERR_SSL_PROTOCOL_ERROR message in Chrome. If this is the case, all you have to do is clear the cache to rectify the error.

In Chrome, simply open the settings menu by clicking on the three dots in the top right-hand corner and choose the 'Settings' option from the drop-down menu.

Image: Google Chrome: Settings
You can also access the settings menu with your mobile device by clicking on the three dots.

Click the 'Advanced' button to access the 'Privacy and security' options. There you will find what you’re looking for – 'Clear browsing data', which you can use to delete the Chrome cache.

Tip

You can also access the cache delete menu in an even quicker way by entering the following address as the URL: chrome://settings/clear­Browser­Data.

Image: Chrome: Clear browsing data
To solve the cer­ti­fic­ate problem, it makes sense to clear the Chrome cache for the entire period and not just for the last few hours.

The SSL cache is managed by the operating system itself, which is why it cannot be deleted using Chrome. You will find the cor­res­pond­ing function in the network and internet setting, which can be accessed in Windows via the control panel.

Image: Windows 7 control panel
In the Network and Internet Control Panel, the most important settings for local networks and the internet can be found on Windows devices.

In 'Network and Internet', you will find 'Internet Prop­er­ties', which you should select. Then click the 'Content' tab, then click 'Clear SSL state'.

Image: Internet options for Windows 7
For most operating systems, such as Windows 7, the SSL cache is referred to as the SSL status.

You receive a status report when the cache has been deleted and you can then check whether the ERR_SSL_PROTOCOL_ERROR problem has been solved by emptying the cache then accessing the site again using Chrome.

Image: Windows status report
The message 'SSL cache was suc­cess­fully cleared' informs users that Windows was able to delete the cer­ti­fic­ate cache as desired.

Solution 4: de­ac­tiv­ate Chrome ex­ten­sions

Just like every internet browser, Google Chrome can be extended with plugins, which add ad­di­tion­al features, games, or new designs to the user interface. However, with each ad­di­tion­al extension, you run the risk of impairing the browser’s func­tion­al­ity and causing error messages such as ERR_SSL_PROTOCOL_ERROR. If the previous solutions haven’t been suc­cess­ful, it might be worth­while to de­ac­tiv­ate the ex­ten­sions until you want to use them again. If the SSL con­nec­tion is then able to be suc­cess­fully es­tab­lished, you know it was the extension that was blocking it. By re­act­iv­at­ing the ex­ten­sions step by step (including doing the con­nec­tion test), you can easily identify what was re­spons­ible.

To access the ex­ten­sions, click on the three dots next to the browser’s search bar, just like when you’re deleting the Chrome cache. From the drop-down menu, select 'More tools', then 'Ex­ten­sions'.

Tip

You can also enter chrome://ex­ten­sions/ into the search bar to go directly to the ex­ten­sions.

Image: Google Chrome menu: 'More tools'
Via the menu item 'More tools', you can access developer tools and the browser’s task manager as well as the Chrome ex­ten­sions.

De­ac­tiv­ate the activated ex­ten­sions one after the other by un­check­ing all the checked boxes, then restart Chrome and check if ERR_SSL_PROTOCOL_ERROR continues to occur when you try to access the target website.

Image: Chrome Extensions
To enable a de­ac­tiv­ated extension in Chrome, all you have to do is check the 'Enable' box next to the relevant extension.

Solution 5: switch off the QUIC protocol

Google Chrome was one of the first browsers to implement QUIC. The future-oriented protocol is intended to provide extra speed when setting up a con­nec­tion, among other things. Of­fi­cially still in the test phase, it is already activated by default as an 'ex­per­i­ment­al protocol' in various services offered by the large cor­por­a­tion such as the Google browser, which means it could be a possible cause for the ERR_SSL_PROTOCOL_ERROR. It is sometimes enough to simply de­ac­tiv­ate QUIC to solve the problem. To do this, first enter the following address in the search bar: chrome://flags/#enable-quic In the Chrome flag menu, all features are listed that have not yet been of­fi­cially im­ple­men­ted in the browser. Here you will see 'Default' chosen, which means that QUIC is active. To switch the protocol off, select the 'Disabled' option and restart Chrome.

Image: Google Chrome: Flag menu
Via Google Chrome, users can access the QUIC protocol on the most popular devices (macOS, Windows, Linux, Android).

Solution 6: delete or reset hosts file to its default setting

Before the Domain Name System (for name res­ol­u­tion on the internet) was in­tro­duced and es­tab­lished, a system based on local text files was used, which had to be main­tained manually. This file named 'hosts' still exists today in common operating systems, but is usually only used for assigning addresses in local networks.

It is, however, possible for malicious programs to modify the hosts file so that you are re­dir­ec­ted to the wrong websites or so that error messages such as ERR_SSL_PROTOCOL_ERROR appear. However, by deleting the file or restoring the default settings (if you have made your own network con­fig­ur­a­tions), you can quickly fix this problem. With Windows, it works like this:

  1. Open the 'Run' program by pressing the Windows key and [R] at the same time.
     
  2. In the new window, specify the directory in which the hosts file is located by inserting the following line (if Windows is not installed on C:, you must use the ap­pro­pri­ate drive letter):

    C:\Windows\System32\drivers\etc
     
  3. Once you’ve confirmed the entry by clicking on 'OK', you will get to the des­tin­a­tion folder where you can select and delete or edit the hosts file. 
Image: Directory of the hosts file on Windows 7
To edit the hosts file, simply open it with the text editor of your choice.

Users of other systems can proceed in the same way (access directory, then delete the file), but the directory path varies from system to system: macOS, Unix, Linux, and Android users can find the hosts file in /etc/hosts. iOS stores the file in the /private/etc/hosts directory.

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