I recommend you to natively manage Windows Firewall. Windows Firewall is based on Windows Filtering Platform, and simplewall is based on Windows Filtering Platform, too. So, basically, what you are doing is just replacing Windows’s native firewall, Windows Firewall, with simplewall. Replacing one firewall with another.
Sure, simplewall is much better [than that miserable and crippled Windows Firewall], but what’s even better is to manage the already existing Windows Firewall natively. This eliminates any potential interference that may arise due to having two firewalls (I personally never had any interferences or problems using simplewall, but I’m unaware if there could be problems in some use-cases, for example), and it’s just a “clean” approach.
Best tool to manage Windows Firewall natively is Windows Firewall Control. It is just as lightweight and simple as simplewall. There are no other decent solutions for managing Windows Firewall natively. The app I linked is closed-source, however the developer is very active on this forum:
Windows Firewall Control (WFC) by BiniSoft.org | Wilders Security Forums
There are some little controversies with simplewall. Online virus scans detect some malware, however highly likely they are just false positives:
VirusTotal scan of simpewall
Hybrid Analysis scan of simplewall
Moreover, simplewall still doesn’t have any digital signature, and the developer doesn’t have knowledge how to sign their software, while this information is publicly accessible. Lack of a certificate is not very important, though desirable.
I also dislike the developer’s attitude, and hence dislike the developer himself:
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I get it that a lot of people created issues asking about malware (which are highly likely just false positives) in his GitHub simplewall project throughout the years, but it is his duty and responsibility to explain to the users of his project that simplewall doesn’t have any malware and that malware detections are false positives. If he has grown sick and tired of having to deal with all these malware-related GitHub issues, the solution would be for the developer to take his time to explain everything in detail and thoroughly only once, in one of these malware-related issues, and then, in the future, when some user creates a yet another malware-related issue, the developer could just put a link to their explanation and close the issue. No problems. He didn’t do that, however.
By answering with “i dont care” you basically say that “I don’t give a single f*** about you, the user of my application”. It is unprofessional, unethical, disrespectful to the user, negligent, and, after all — rude. I personally don’t want to use a software from such a developer. I like his firewall, however. It’s very light on resources and very simple. Windows Firewall Control is very light and simple, as well. Both are good programs. But I recommend Windows Firewall Control for the reasons I mentioned in my first paragraph.
And I partially disagree with anon82677111. They said:
Simplewall does not add anything new that cannot be done with the standard Windows firewall.
Windows Firewall lacks the most important usability feature which almost all people expect from a software firewall: the ability to manage connections interactively, that is: the ability to block everything by default and have Windows Firewall prompt you to allow/block connections on the first connection [of an application]. Windows Firewall can’t do that without relying on a third-party software.
so take my comment with a grain of 
