Outbound traffic

Sandboxes send from the addresses listed at withruntime.com/egress.json, IPv4 and IPv6, with the time the list last changed. The list changes when a server joins or leaves, so read it rather than copy it once.

Terminalcurl -s https://withruntime.com/egress.json# {"ipv4":["203.0.113.10", ...],"ipv6":["2001:db8::10", ...],"updatedAt":"..."}

An account can hold its own address, which no other account sends from (Dedicated outbound addresses). To admit one customer and nobody else, ask them for theirs.

An account can have its sandboxes sign their HTTP requests as Runtime's, with Web Bot Auth (RFC 9421 HTTP message signatures). A site, or Cloudflare, Akamai or Vercel in front of it, can then tell an agent on Runtime from anonymous traffic on a hosting network. It is off until the account turns it on.

• Signature-Agent is "https://withruntime.com". Runtime's keys are at withruntime.com/.well-known/http-message-signatures-directory.
• Each signature covers the site's authority and the Signature-Agent header, and lasts 5 minutes.
• Only from a running sandbox of an account that turned it on. Runtime never gives the key to a sandbox.

• Mail. Ports 25, 465 and 587 are closed to every sandbox. Support opens them for an account only on request, after review.
• Scans. A sandbox that tries many ports or many addresses the way only a scanner does has its network turned off.
• Private addresses. Private, internal and link-local addresses are refused, whoever asks.
• Floods. Each sandbox has limits on connections opened a second, on upload speed and on bytes a day; each account has limits on top.

Every outbound connection is recorded against the sandbox and the account that made it, so a report with an address and a time finds its sender.

Write to abuse@withruntime.com with the address or URL involved, the date, time and time zone, and any logs you have. We find the sandbox, cut its network and act on the account.