Currently I'd trust dillo for https about as much as I'd trust wget for https. (Not that I've really examined wget, but just as a sort of gauge here...) Back in the DPI days, dillo didn't check hostnames on certificates because that was an impossible nightmare with openssl unless you found the code somewhere to modify for your own project. [By the way, there was outrage a couple of years ago when people realized that lots and lots of tools out there, and tls libraries for popular languages, were using OpenSSL and not doing any hostname validation.] It was only with 3.0.5 that I had looked into TLS myself and learned enough about what's insecure at present to disable old ciphers, disable ssl3, disable tls compression. When TLS moved into the browser with the OpenSSL version, I integrated hostname checking code adapted from wget source. And now mbed TLS does the checking itself. At present, our weakness relative to something like chrome or firefox would be in the area of certificate revocation. Dillo has never had a way to know when a certificate has been revoked. For a while, there were certificate revocation lists (CRLs) that are generally published by the assorted certificate authorities, although sometimes you have to click on agreements to get them. The other problem is that those grow _huge_, and distributions don't generally have packages for them (unlike ca-certificates for root certificates). I wouldn't be surprised if the agreements bar distribution. And there was OCSP, which stands for.... Online Certificate Status Protocol. Every time you get a certificate, you query some server, often a third-party server, and ask it whether this certificate is still valid. But those OCSP servers were/are nowhere near reliable enough, and browsers couldn't very well fail everything when the OCSP servers were being flaky.. So OCSP stapling has been coming along, where the OCSP data comes from the original server along with the certificate. OpenSSL has had OCSP code for a little while, but it's very buggy and not documented, and maybe you could get it to work if your application is exceedingly similar to the sample client, but good luck. mbed TLS has OCSP on their roadmap, but it's not implemented yet. As for what the firefoxes and chromes of the world are up to, firefox ripped out their CRL code a while back and they have some other mechanism where certificate authorities notify them of revocations and they push it out. Because they're still big enough to get certificate authorities to do things for them. And they have 'public key pinning' where a server sends keys to certificates, and the client checks that, when certificates are presented in the future, they continue to use one or more of those keys. My understanding is that this is not at all widely used currently. Like if you go to google while claiming that you're chrome, maybe.