Heroku: Application platform

What Heroku is

Heroku is a managed platform that runs applications in containers called dynos, with a routing layer in front that terminates TLS and distributes requests. Applications receive a herokuapp.com hostname, and custom domains are attached through a DNS target rather than a fixed address. Most Heroku deployments run on AWS infrastructure, so the announcing network usually belongs to Amazon rather than to Heroku.

How DNSTrace.dev detects it

Detection correlates independent public signals. A single match is reported as strong evidence; agreement between a response header and the announcing network is reported as confirmed.

via containing vegur — Vegur is the Heroku router's HTTP proxy, and it names itself in the via header.
server: Heroku — Emitted by parts of the Heroku routing layer.
CNAME targets under herokudns.com or herokuapp.com — The standard Heroku custom-domain mapping.
AS16509 — The Amazon autonomous system underneath most Heroku regions, which is why ASN alone cannot identify Heroku.

What a detection proves

The request passed through the Heroku router before reaching an application dyno.

What it does not prove

Which application language or framework runs in the dyno, or which AWS region hosts it. DNSTrace.dev reports the framework separately when the application declares one.