simplex.im
Mostly blocked
15 of the 18 URLs we have a verdict for under simplex.im are blocked in mainland China; 3 are not. The site itself, https://simplex.im, is blocked. The Great Firewall silently drops its packets so requests time out, breaks its TLS handshake and poisons its DNS. 294 tests have been run under this domain since 2023-07-31, the most recent on 2026-08-16.
The site itself
https://simplex.imas of 2026BlockedPages and subdomains (17)
http://smp4.simplex.imBlockedhttp://smp11.simplex.imBlockedhttp://smp15.simplex.imBlockedhttp://smp10.simplex.imas of 2026Blockedhttp://Smp12.simplex.imBlockedhttp://Smp14.simplex.imas of 2026Blockedhttps://smp15.simplex.imas of 2026Intermittenthttps://Smp14.simplex.imas of 2026Blockedhttps://Smp11.simplex.imas of 2026Blockedhttps://Smp16.simplex.imas of 2026Blockedhttps://Smp17.simplex.imas of 2026Blockedhttps://Smp18.simplex.imas of 2026Intermittenthttps://Smp19.simplex.imas of 2026Intermittenthttps://xftp1.simplex.imas of 2026Blockedhttps://xftp2.simplex.imas of 2026Blockedhttps://xftp3.simplex.imas of 2026Blockedhttps://xftp6.simplex.imas of 2026BlockedAbout simplex.im and the Great Firewall
15 of the 18 URLs we have a verdict for under simplex.im are blocked in mainland China; 3 are not. The site itself, https://simplex.im, is blocked. The Great Firewall silently drops its packets so requests time out, breaks its TLS handshake and poisons its DNS. 294 tests have been run under this domain since 2023-07-31, the most recent on 2026-08-16.
A VPN or another circumvention tool routes the request outside mainland China, past the filtering that blocks simplex.im. GreatFire runs GreatFire VPN; the Analyzer also tests the domains of many VPN and proxy providers, so you can check whether one is reachable before relying on it.
Elsewhere on the site
Each URL's status is its verdict over the last 90 days, the same one its own page headlines.