Defaults.Exposed › Stats › TLS & certificates
How many websites use self-signed certificates?
October 2026 census edition
As of October 12, 2026, 4,390,979 domains in the Defaults.Exposed census present a self-signed certificate: 2.0% of the 220.3 million domains presenting any certificate.
Raw-pass counts include roughly 1% re-scan duplicates; proportions are unaffected.
Self-signed certificates: how it is measured
It comes from the certificate-validation pass, which attempts a full chain validation against the public trust stores and records what failed when it did. Every domain in the census is measured directly and counted once.
A self-signed certificate encrypts the connection and proves nothing about who is on the other end, which is the half of TLS (Transport Layer Security) that actually stops interception. Every visitor sees a browser warning, which teaches them to click through the same warning when it signals a real attack.
The figure is an absolute count of domains rather than a sample scaled up. A domain the census could not decide on is left out rather than estimated.
It moves when hosts enable HTTPS (Hypertext Transfer Protocol Secure), renew or misconfigure certificates, and when platforms change what they negotiate by default. Most of the movement here comes from platform defaults. The number is recomputed from the raw evidence at every edition. What it cannot tell you is where one particular domain stands: for that, see fix your TLS setup.
the full grading methodology · the underlying dataset, published open with the counts behind every percentage. If a figure here disagrees with one elsewhere on the site, the dataset is canonical and we would like to know.
Self-signed certificates: how to cite it
Please cite Defaults.Exposed and link this page. The citation below carries the date.
Defaults.Exposed, "How many websites use self-signed certificates?" (as of October 12, 2026). https://defaults.exposed/stats/how-many-websites-use-self-signed-certificates
Permalink: https://defaults.exposed/stats/how-many-websites-use-self-signed-certificates · Machine-readable: /stats/s/self-signed-certs.json · Licence: open data
Methodology: how we grade the internet · Source data: census data and downloads. Updated with each census edition.